Provided is a transmission circuit 1 which is capable of precisely compensating for an offset characteristic of an amplitude modulation section 15, and operating with low distortion and high efficiency over a wide output electric power range. A signal generation section 11 outputs an amplitude signal and an angle modulation signal. An amplitude amplifying section 14 inputs, to the amplitude modulation section 15, a signal corresponding to a magnitude of the amplitude signal having been inputted. The amplitude modulation section 15 amplitude-modulates the angle modulation signal with the signal inputted from the amplitude amplifying section 14, and outputs a resultant signal as a modulation signal. The power measuring section 18 measures an output power of the amplitude modulation section 15. An offset compensation section 12 reads an offset compensation value from a memory 13 in accordance with the output power of the amplitude modulation section 15, and adds the read offset compensation value to the amplitude signal.