A transmission circuit operates with high efficiency and low distortion. An amplitude and phase extraction section extracts amplitude data and phase data from input data. A phase modulation section phase-modulates the phase data to output a resultant signal as a phase-modulated signal. An amplifier section amplifies the phase-modulated signal to output a resultant signal as a transmission signal. An amplitude control section supplies, to the amplifier section, a voltage controlled in accordance with an AC component represented by a fluctuation component of the amplitude data and a DC component represented by an average value level of the fluctuation component of the amplitude data.