To realize a control method for preventing deterioration in a power amplifying element 3 by holding the temperature decrease gently when power amplifying operation of a power amplifier 7 is stopped, in order to solve the problem in the conventional device that the power amplifying element 3 generates a sudden increase in the heat, so that sharp temperature change is generated when the power amplifier 7 stops its operation, and element deterioration is apt to be caused, and reliability is hardly ensured.

A temperature sensor 10 is installed in the vicinity of the power amplifying element 3 in the power amplifier 7. A temperature is observed at a constant period. The temperature change is inputted in a decision circuit 11 in a control unit 8. Operation control of a fan 1 for cooling is performed according to the temperature change, thereby making the temperature change gentle when the power amplification operation is stopped.