To provide a light-weight, compact, and low cost HPA device which corresponds to increase and decrease of rainfall attenuation.

Power is combined using first and second amplifiers, and a power combiner and a switcher are disposed on the output side. Output power is controlled to about 1/10 of the maximum power in a single tube operation mode when the rainfall attenuation is small in clear weather. In the device output value changing method during rainfall, reception level of a beacon signal from a satellite is monitored, and when the line disconnection standard is approached, full power is transmitted by operating two TWTs. Furthermore, in order to level the ratio of operation of the first and second amplifiers, the amplifier to be used is changed periodically, thus achieving long life of the device.