A transmitter circuit is provided which is capable of reducing modulation distortion even when an output power of a power amplifying section 141 is low. A signal generation section 11 generates an amplitude signal and a phase signal. A regulator 12 outputs a current based on the amplitude signal. A phase modulation section 13 phase-modulates the phase signal, and outputs a phase-modulated signal. The power amplifying section 141 receives the current which is based on the amplitude signal and supplied as a bias current from the regulator 12, and amplifies the phase-modulated signal by using the supplied current. Further, to the power amplifying section 141, a predetermined DC voltage is supplied as a collector voltage.