in press molding or embossing a thermoplastic resin for producing a molded product excellent in transferability of microscopic surface asperities and having high quality with high productivity , a preform of a thermoplastic resin is heated to about the hardening temperature of the thermoplastic resin constituting the preform . the preform is embedded between an upper half and a lower half of a mold which are maintained at a temperature of about the hardening temperature of the thermoplastic resin , and then the mold is closed at a low pressure . carbon dioxide is dissolved in a surface of the preform by charging carbon dioxide between a surface of the mold and the surface of the preform in order to reduce the viscosity of the preform surface . the surface of the mold is brought into contact with the preform having the reduced surface viscosity by increasing a pressing pressure . then , carbon dioxide is discharged , and a molded product is extracted . thus , the molded product excellent in transferability of microscopic surface asperities and having high quality can be produced with high productivity .