Summary: This paper describes a millimeter-wave pulse transmitter with a 38 GHz-band Voltage Controlled Oscillator (VCO) and a 77/38 GHz-band harmonic mixer. This harmonic mixer works as both of a pulse modulator and a multiplier. This configuration of the transmitter is very simple, and can be applied to high-speed pulse modulation like Ultra Wide Band. By using the harmonic mixer, furthermore, a fluctuation of the load impedance of the 38 GHz VCO can be reduced. Compared with the conventional configuration, the required amount of isolation between the VCO and the load has been able to be reduced by more than 30 dB as a result of the experiment in a millimeter-wave band.