A transmission circuit for outputting transmission signals with a low distortion and a high efficiency over a wide range of output power is provided. A signal generation section (11) generates an amplitude signal and a phase signal. An angle modulation section (12) performs angle modulation on the phase signal and outputs an angle-modulated signal. A regulator (14) receives the amplitude signal via a variable gain amplification section (18) and supplies a voltage controlled based on the magnitude of the amplitude signal to the amplitude modulation section (15). The amplitude modulation section (15) performs amplitude modulation on the angle-modulated signal and outputs a modulated signal to the variable attenuation section (16). When the value of power information is smaller than a predetermined threshold value, the control section (19) increases the gain of the variable gain amplification section (18) and the attenuation of the variable attenuation section (16).