There are provided a method of producing an SOI wafer of high quality with excellent controllability, productivity and economy and a wafer produced by such a method. In the method of producing a substrate utilizing wafer bonding, a first substrate member and a second substrate member are mutually bonded, and then the second substrate member is separated from the first substrate member at the interface of a first layer and a second layer formed on the main surface of the first substrate member, whereby the second layer is transferred onto the second substrate member. In the separation, the separation position at the interface of the first and the second layers is ensured by varying the porosity of a porous Si layer, forming an easily separable plane by the coagulation of pores in porous Si, effecting ion implantation to the interface or utilizing a heteroepitaxial interface.