To omit a detector circuit and accordingly to omit a feedback loop in order to obtain a small and lightweight APC circuit by applying the corresponding gain control voltage decided from the detected signal of a temperature sensor based on the memory contents of a storage part to an automatic gain control amplifier.

An RF signal is inputted to an automatic gain control amplifier 1, and an output signal is inputted to a shared device 3 via a power amplifier 2. In a series of this flow, the output levels of the amplifiers 1 and 2 vary in response to the change of temperature and frequency since both amplifiers 1 and 2 have the temperature and frequency characteristics. In this respect, the ambient temperature is detected by a temperature sensor 7 and inputted to a control part 9 as a digital signal. The part 9 outputs an appropriate gain control voltage signal based on the received digital signal and the data stored in a 1st storage part 8. The digital output signal received from the part 9 is converted into an analog signal by a D/A converter 5 and inputted to the amplifier 1. Thus, the varying output level depending on the change of the ambient temperature can be always kept constant.