A RF power amplifying device is constituted by a system of a balanced amplifier including first phase shifters, a first RF power amplifier, a second RF power amplifier, second phase shifters, and a power combiner. Transmitting power Pout is detected by a first power level detector connected to an output of the first RF power amplifier, a second power level detector connected to an output of the second RF power amplifier, and an adder. A level control signal from a level control circuit controls transmitting power in response to a transmitting signal with wanted power level and a detected signal of the adder.