There is disclosed a method of fabricating an SOI wafer by a hydrogen ion delamination method wherein a surface of an SOI layer is not polished but is subjected to heat treatment in a reducing atmosphere containing hydrogen after a bonding heat treatment, a method of fabricating an SOI wafer by a hydrogen ion delamination method wherein a surface of an SOI layer is not polished but subjected to heat treatment in a reducing atmosphere containing hydrogen after delaminating heat treatment, and a SOI wafer fabricated by the methods. There are provided a method of fabricating an SOI wafer by a hydrogen ion delamination method wherein a damage layer remaining on the surface of the SOI layer after delamination is removed and surface roughness is improved without polishing, so that uniform thickness of the SOI layer can be achieved, and to simplify the process therefor.