A method for press molding a thermoplastic resin which includes the steps of supplying a resin melt in a cavity of an unclosed mold through at least one passage formed in a wall of the mold upper and lower halves of which are respectively attached to upper and lower platens of a vertically movable press so that the supplied resin melt contacts with surfaces of the upper and lower halves of the mold, pressing the resin melt in the mold by closing the mold so that the mold closing is still being carried out after the supply of the resin melt is finished or the mold closing is started at the same time as the supply of the resin melt is finished, and then cooling the molded resin in the mold.