The fact that Jesus’ tomb was found empty is reported early, by multiple sources, by eyewitnesses, and with non-Christian corroboration. Thus:
"Former Oxford University church historian William Wand writes, 'All the strictly historical evidence we have is in favor of [the empty tomb], and those scholars who reject it ought to recognize that they do so on some other ground than that of scientific history.'" (Gary Habermas and Michael Licona, The Case For The Resurrection Of Jesus [Grand Rapids, Michigan: Kregel Publications, 2004], p. 73)
"Without addressing Jesus’ resurrection appearances, Vermes 1973: 41, another Jewish scholar closely acquainted with the primary evidence, opines that 'the only conclusion acceptable to the historian' must be that the women actually found the tomb empty." (Craig Keener, A Commentary On The Gospel Of Matthew [Grand Rapids, Michigan: William B. Eerdmans Publishing Company, 1999], p. 705, n. 308)
The large majority of scholars accept the empty tomb as a historical fact. See, for example, here.
Testimony to the empty tomb is found in every gospel and Acts, and it’s mentioned or implied in other sources. The accounts have some common elements, including details unlikely to have been fabricated. The tomb is first found empty by women, and the testimony of women was largely considered of little value in that culture, while the male disciples are in hiding and unbelief. The burial is associated with an individual, Joseph of Arimathea, who is named, has a prominent place in Jewish society, and belongs to a group that the early Christians wouldn’t have wanted to compliment with such an account (the religious leaders of Israel who had Jesus crucified and were persecuting the early church). The early Jewish opponents of Christianity affirmed that the tomb was empty (Matthew 28:11-15; Justin Martyr, Dialogue with Trypho, 108; Tertullian, On Spectacles, 30). Contrary to what some people claim, Justin Martyr and Tertullian aren’t just repeating what they read in Matthew’s gospel. Both of them give details in their accounts that aren’t mentioned by Matthew, and both Justin and Tertullian were interacting with the Jewish opponents of their day, so they would have been in a position to know what arguments the Jewish opposition was using.
Sometimes people ask why we don’t know where Jesus’ tomb was if His burial place was known to the early Christians. But we do have a good idea of where the tomb was:
"That Jesus' followers would forget the site of the tomb (or that officials who held the body would not think it worth the trouble to produce it after the postresurrection Jesus movement arose) is extremely improbable. James and the Jerusalem church could easily have preserved the tradition of the site in following decades (Brown 1994: 1280-81), especially given Middle Eastern traditions of pilgrimage to holy sites (though admittedly evidence for early veneration there is lacking, perhaps because the body was not there – Craig 1995: 148-49, 152)….the Catholic Holy Sepulchre and tombs in its vicinity date to the right period. The tradition of the latter vicinity [Holy Sepulcher] is as early as the second century (when Hadrian erected a pagan temple there; he defiled many Jewish holy sites in this manner – cf. Finegan 1969: 164), and probably earlier. Good evidence exists, in fact, that this site dates to within the first two decades after the resurrection. This is because (1) Christian tradition is unanimous that Jesus was buried outside the city walls, and no one would make up a site inside (cf. Heb 13:12; Jn 19:41); (2) Jewish custom made it common knowledge that burials would be outside the city walls (4 Bar. 7:13; Wilkonson 1978: 146); (3) the traditional vicinity of the Holy Sepulcher is inside Jerusalem’s walls; (4) Agrippa I expanded the walls of Jerusalem sometime in the 40s A.D." (Craig Keener, A Commentary On The Gospel Of Matthew [Grand Rapids, Michigan: William B. Eerdmans Publishing Company, 1999], p. 695)
Some people argue that the earliest Christians may have believed in a resurrection involving an exchange of bodies, with the old body remaining in the tomb, rather than a transformation of the body in the tomb. Or they suggest that the early Christians might have believed in the resurrection without ever examining the tomb to see whether it was empty. But both scenarios are highly unlikely:
"And although Jesus might have been embodied in a new body, this was not a possibility that would readily have occurred to first-century Jews; they would have expected his embodiment to go with an empty tomb. But if the Gospel writers felt that a Resurrection required an empty tomb, presumably Christians of a decade or two earlier would have felt the same – St Paul would have felt that. So if there was a belief held by anyone in the Church or outside it that the body of Jesus still lay in its tomb, surely St Paul would have felt the need to explain how really the fact that the body was still in the tomb made no difference to Resurrection faith. Those whom he is addressing in 1 Corinthians who held that 'there is no resurrection of the dead' would have had an argument to support them - even Christ’s body was still in the tomb - which would need to be answered. But of course there is none of that in 1 Corinthians or anywhere else in the New Testament (and no evidence of later deletions of any such passages)….it beggars belief that the disciples could have affirmed the Resurrection of Jesus without checking the tomb as soon as they could" (Richard Swinburne, The Resurrection Of God Incarnate [New York: Oxford University Press, 2003], pp. 160-162)
We have good reason to believe that the account of a guard at the tomb is historical, so how could the body have been removed with a guard there? If the early opponents of Christianity knew of a common practice involving the transfer of a body from one tomb to another, and they thought that such a transfer might have occurred with Jesus, why didn’t they say so instead of using the argument that the disciples stole the body?
In a debate on the resurrection with Gary Habermas in April of 2000, Antony Flew, who at that time was an atheist, replied to Habermas’ presentation of the historical evidence for the empty tomb:
"I don’t think you should be apologetic about this at all. These facts are facts and I could rather wish that in these topics more people were prepared to face facts rather than run away and say, 'Mustn’t say that.' No. This is a very impressive piece of argument, I think…Because, you know, it’s very difficult to get around this….Well, we have no independent witnesses. There are all sorts of ways of removing bodies. I’m not going to offer a theory because I simply don’t think one can reconstruct the story of what happened in the city and all that long ago and we haven’t got the sort of evidence that one might have today with the invention of cameras and all the rest of it….I don’t offer anything to cover the empty tomb evidence." ("Did Jesus Rise From The Dead?" [Chattanooga, TN: Ankerberg Theological Research Institute, 2000], pp. 17-18)