Processes for producing polycarbonate by solid phase polymerization which simplify the crytallization to be conducted prior to the solid phase polymerization to thereby permit further shortening in the treatment time. A process for producing polycarbonate is characterized in that an amorphous polycarbonate prepolymer prepared by transesterification of aromatic dihydroxy compound with a diester of carbonic acid is prepolymerized in a solid phase under an atmosphere containing gaseous swollen solvent while the prepolymer is kept in a fluid state. Another process for producing polycarbonate is characterized in that a mixture comprising an amorphous polycarbonate prepolymer prepared by transesterification of an aromatic dihydroxy compound with a diester of carbonic acid and a polycarbonate prepolymer which has undergone crystallization is prepolymerized in a solid phase under an atmosphere containing a gaseous swollen solvent.