A method for preparing a substrate sheet for an optical recording medium has the steps of controlling a roll stamper having a preformat pattern on the peripheral surface thereof and a molding roll disposed with a predetermined gap between the same and the roll stamper so that they have a predetermined temperature, feeding a thermoplastic resin heated to a predetermined temperature to the gap from a means for extruding the thermoplastic resin disposed on the upstream side of the gap, while the roll stamper and the molding roll are rotated at a predetermined rotational frequency, and then molding the thermoplastic resin into a sheet by pressing the resin between the roll stamper and the molding roll to transfer the preformat pattern to the resin. The method is characterized in that the molding is carried out under molding conditions regulated so that continuously measured gap temperatures of the substrate sheet may periodically fluctuate in a predetermined amplitude and so that the amplitude may accord with a previously set value of an amplitude corresponding to a desired transfer precision and birefringence value of the substrate sheet for the optical recording medium.