To provide a reinforcing jig attaching the rotary direction start end part and final end of a stamper and permitting the relative movement of the stamper in the peripheral direction of the roller of the stamper and absorbing the elongation of the stamper when the elongation of the stamper is generated to prevent the levitation of the stamper at the final end part of the roller.

A reinforcing jig 4 mounting a stamper 2 on a heat roller 6 is constituted of an auxiliary main body 14 and a movable element 18. The end surface 1402 in front of the rotary direction of the auxiliary jig main body 14 is formed into a flat surface along the radius direction of the heat roller 6 and the rotary direction start end part 202 of the stamper 2 is attached to the end surface 1402 in front of the rotary direction by a screw 12. The rotary direction rear end part 204 of the stamper 2 is fixed to the end surface 1804 of the movable body 18 by a screw 16. The movable body 18 to which the rotary direction end part 204 of the stamper 2 is fixed is relatively moved in a load acting direction along the outer peripheral surface 6A of the heat roller 6, that is, in the direction separated from the end surface 1404 of the auxiliary jig main body 14.