A transmission circuit is capable of precisely compensating for an offset characteristic of an amplitude modulation section, and operating with low distortion and high efficiency over a wide output electric power range. A signal generation section outputs an amplitude signal and an angle modulation signal. An amplitude amplifying section inputs, to the amplitude modulation section, a signal corresponding to a magnitude of the amplitude signal having been inputted. The amplitude modulation section amplitude-modulates the angle modulation signal with the signal inputted from the amplitude amplifying section, and outputs a resultant signal as a modulation signal. The power measuring section measures an output power of the amplitude modulation section. An offset compensation section reads an offset compensation value from a memory in accordance with the output power of the amplitude modulation section, and adds the read offset compensation value to the amplitude signal.