A method for producing a bonded SOI wafer, by ion implantation delamination to fabricate a bonded SOI wafer having a BOX layer and a SOI layer on a base wafer. After performing flattening heat treatment in an argon gas-containing atmosphere, sacrificial oxidation treatment adjusts the film thickness of the SOI layer, wherein the film thickness of the BOX layer is 500 nm or more. A sacrificial oxide film is formed so the relationship between the film thickness of the SOI layer on the sacrificial oxidation treatment is performed. The film thickness of the sacrificial oxide film formed by the sacrificial oxidation treatment satisfies 0.9d>t>0.45d. A method for producing a bonded SOI wafer can prevent the generation of particles from the outermost peripheral part, which is the form of an overhang by flattening heat treatment, of a SOI layer in the production of a bonded SOI wafer.