A method for plastic sheet manufacturing whereby a layered body including a film is made to pass through a nip portion formed by a pair of belts, each having a joint portion, causing the layered body to be integrated to manufacture a plastic sheet. Before integration, the position of each of the joint portions is detected and the timing at which the layered body enters the nip portion is controlled in accordance with the detected positions. A plastic sheet manufacturing apparatus implements the plastic sheet manufacturing method.