To simply perform the manufacturing of a lenticular lens and the preparing a stereoscopic image using the lens by means of a simple thermal head printer.

A thermal foaming transparent film is periodically heated by the thermal head 5 of a thermal printer and a rugged lenticular lens 8 is simply formed by using the thermal printer. At the same time, a stereoscopic image is simply formed so as to print an image for right eye and an image for left eye synchronized with the ruggedness of the lenticular lens 8 based on a ruggedness position signal for detecting the rugged position of the lenticular lens 8 thus obtained by using the thermal printer.