A transmission circuit includes a transmission signal generation unit, a control unit, and a transmission signal amplification unit. The transmission signal generation unit generates a transmission signal that has been modulated. The transmission signal amplification unit includes a power amplifier that amplifies the transmission signal. The control unit determines a supply voltage signal having an amplitude characteristic of a period identical to that of an envelope of the transmission signal and supplies the supply voltage signal to the power amplifier. The control unit determines an output timing of the supply voltage signal such that a phase difference between a phase of the envelope of the transmission signal and a phase of the supply voltage signal does not become zero.