Provided is a pulse modulation circuit that improves the on/off operation and improves the on/off ratio of an output power of the entire pulse modulation circuit in the switching operation. The pulse modulation circuit inputs a local oscillation wave and a DC pulse signal, mixes a second harmonic wave of the local oscillation wave with the DC pulse signal, and outputs an RF pulse signal. The pulse modulation circuit includes: a switch that inputs the local oscillation wave and attenuates the local oscillation wave at an off time more than at an on time; and a harmonic mixer that inputs the local oscillation wave affected by the switch and the DC pulse signal, mixes the second harmonic wave of the local oscillation wave with the DC pulse signal, and outputs the RF pulse signal, in which the switch is allowed to conduct the switching operation together with the harmonic mixer according to the DC pulse signal.