Abstract: A thermoplastic sheet is prepared by (i) extruding a molten thermoplastic resin in the form of a sheet from a molding die; (ii) applying static charges to the extruded resin sheet from a first electrode whereby the charged resin sheet is pinned to the surface of an electrical insulating layer of a quenching roller to quench the resin sheet; (iii) peeling the quenched sheet from the surface of the quenching roller; and (v) applying electrostatic charges having a reverse polarity to that of the electrostatic charges from the first electrode to the exposed surface portion of the quenching roller from a second electrode. The quenching roller is made of an electrically earthed substrate and the electrical insulating layer formed on the surface of the substrate.