the invention provides an imprinting jig for transferring a pattern onto a thermoplastic sheet . the imprinting jig is provided with : a first die having a surface with a pattern ; a die holder for supporting the first die ; an elastic member placed between the first die and the die holder ; and a second die opposing to the first die . the thermoplastic sheet is placed on the surface with the pattern of the first die . the imprinting jig optionally includes an adhesion reducing means between the elastic member and the first die or between the elastic member and the die holder .