An apparatus and method for manufacturing a substrate sheet for information recording mediums having a roll stamper consisting of a flexible stamper having a pattern corresponding to a preformat for an information recording medium, the flexible stamper being fixed along the corresponding periphery of a roll substrate. A roll is placed opposite the roll stamper. A molten-resin sheet wider than the flexible stamper member is formed. The apparatus has means for bringing the edges of a resin sheet into contact with the roll substrate before releasing the resin sheet from the roll stamper. The temperature is controlled, so that a temperature difference on the surfaces of edges of a resin sheet and a preformat pattern transfer area of the resin sheet is kept within 30.degree. C. when the resin sheet is separated from the roll stamper after the molten-resin sheet has been pressed between the roll stamper and roll.