The present invention provides a method of producing an SOI wafer, comprising at least steps of forming an oxygen ion-implanted layer by implanting oxygen ions into a silicon wafer from one main surface thereof, subjecting the silicon wafer to oxide film-forming heat treatment to convert the oxygen ion-implanted layer into a buried oxide film, and thereby producing an SOI wafer having an SOI layer on the buried oxide film, wherein when the buried oxide film is formed in the silicon wafer, the buried oxide film is formed so that a thickness thereof is thicker than a thickness of the buried oxide film which the SOI wafer to be produced has, and thereafter the silicon wafer in which the thicker buried oxide film is formed is subjected to a heat treatment to reduce the thickness of the buried oxide film. Thereby, there can be provided a method of producing an SOI wafer in which a high quality SOI wafer having a buried oxide film of which a film thickness is thin and perfectness is high and an SOI layer of which crystallinity and surface quality are extremely good can be produced by using SIMOX method.