PURPOSE: To miniaturize a device by directly connecting a power summing part to a matching part, and receiving them in a matching device.

CONSTITUTION: A RF signal transmitted from an oscillator 1 is divided by a power divider 3 and then transmitted to first and second power amplifiers 4a, 4b, respectively. The RF power amplified by the amplifier 4a, 4b is sent to, for example, a matching device 6 of impedance 50Ω. Therefore, the output impedance of a synthesizer 6 is, for example, 25Ω, and the output power is 1/(root 2) according to the equation of W=V2/R when the passed voltage is equal. Thus, the voltage resistance of a parallel capacitor 622 is 1/(route 2) in the case of the matching device of impedance 5Ω, allowing the miniaturization. Since a power summing part 61 and a matching part 62 are directly connected to each other and received in a matching device 6, a circuit for converting the output impedance of the summing part 61 is not required. The withstand voltage of the matching device 61 is also reduced.