Abstract: This invention relates to a method of fabricating a bonded wafer 39 in which a bond wafer 31 and a base wafer 32, both of which are composed of silicon single crystal, are bonded while placing an oxide film 33 in between, and the bond wafer 31 is thinned. Use of modified chemically-etched wafers as both of the bond wafer 31 and base wafer 32 is successful in reducing an unbonded area UA therebetween after annealing for bonding, where the modified chemically-etched wafer refers to a wafer which is etched by alkali etching and succeeding acid etching, while setting etching amount larger in the alkali etching than in the acid etching.