An object of the present invention is to suppress to a sufficiently small level variation in the temperature of an object in a case where the temperature of an object is controlled to a desired value using 
heat transfer fluid. A controller (9) controls the power of a 
thermoelectric conversion device (6) which is used for cooling or heating 
heat transfer fluid supplied to an object (5). The controller (9) performs a 
feedback control operation using the temperature (T1) of the 
heat transfer fluid emitted from the 
thermoelectric conversion device (6) and the temperature (Ts) of the object. In this 
feedback control operation, the difference between the object temperature (Ts) and the heating medium temperature (T1) is added to a set temperature (SV), whereby a target temperature of the heating medium temperature (T1) is calculated. By means of an I-PD calculation with respect to the deviation between this target temperature and the heating medium temperature (T1), a manipulated variable to be applied to the cooler / heater (6) is calculated. Prior to the beginning of this 
feedback control operation, an initial value of the aforementioned manipulated variable is calculated in accordance with the magnitude of a 
thermal load to be applied to the object (5) from outside during the control operation and the set temperature (SV). The feedback control operation begins upon the output of this initial value.