PURPOSE: To increase a heat transmitting quantity between a pressure medium and belts by preparing an elastically pressurized member toward the inside of the press belts in a pressure chamber and additionally connecting a material having excellent heat transmission to a member body to enlarge its surface area.

CONSTITUTION: In the internal part of a pressure chamber 14, a member elastically pressurized toward the inside of press belts 8, 9 is composed of a body 27 and a surface enlarging part 34. The surface enlarging part 34 is made of a material having excellent heat transmission and is connected to the body 27 so as to excellently transmit heat. The enlarging part 34 is protruded toward a fluid pressure medium in the pressure chamber 14. Thus, a great quantity of heat is transmitted between the fluid pressure medium in the pressure chamber 14 and the press belts 8, 9.