An object of the present invention is to provide a practical and low-cost method of reducing cold spots generated on the heating face of a ceramic susceptor and the temperature distribution on the heating face when the supporting portion is joined with the susceptor at the back face and is fitted to a chamber through a cooling system. A supporting portion 6 is joined with the back face of a ceramic susceptor. An inner space 6f separated from atmosphere in a chamber is formed. A cooling system is provided between the supporting portion 6 and chamber. Thermal control portions 12A and 12B are provided between the cooling system and supporting body 6 for reducing thermal conduction from the susceptor to the cooling system.