There is provided a bonded wafer having excellent thickness uniformity after thinning but also good surface roughness and being less in defects.In the production method of a bonded wafer by bonding a wafer for active layer to a wafer for support substrate and thinning the wafer for active layer, oxygen ions are implanted into the wafer for active layer to form an oxygen ion implanted layer in the active layer and thereafter a heat treatment is carried out in a non-oxidizing atmosphere at a temperature of not lower than 1100° C., and an oxide film formed on the exposed surface of the oxygen ion implanted layer is removed and then a heat treatment is carried out in a non-oxidizing atmosphere at a temperature of not higher than 1100° C.