To allow the temp. in a chamber to rapidly arrive at objective temp. and to stabilize the same at the objective temp.

A temp. sensor 21 outputs the temp. detection signal corresponding to the detected temp. at the predetermined position within a chamber capable of obtaining the temp. change curve almost proportional to the temp. change curve at the position where predetermined temp. must be controlled within the chamber to a heating control means and the heating control means heats the chamber on the basis of the temp. detection signal and also outputs a heating control signal in order to keep detected temp. constant after the detected temp. arrives at objective temp. to control a heater 23. Therefore, the temp. in the chamber can be rapidly raised to objective arrival temp. and, after the temp. reaches the objective arrival temp., this state can be stably held and measuring accuracy can be enhanced and a time required in measurement can be shortened.