A voltage controlled oscillator outputs an output signal whose frequency corresponds to inputted control voltage. A distributor distributes the output signal outputted from the voltage controlled oscillator. A plurality of injection-locked oscillators regulate self-oscillation frequencies according to the above frequency and output signals obtained by frequency-multiplying signals distributed by the distributor. A combiner combines and outputs the signals outputted from the plurality of injection-locked oscillators. This makes it possible to increase output power while preventing an operating band from narrowing.