To reduce the carrier wave leakage during a transmission output by applying an oscillation signal to the output signal of a modulation circuit so as to cancel a carrier wave leakage component in the output signal of a modulation circuit.

After the common-mode component I outputted from a base band signal generator 1 is passed through a subtracter 2, the component is multiplied by the oscillation signal outputted from an oscillator 6 in a mixer 4. After the orthogonal component Q outputted from a base band signal generator 1 is passed through a subtracter 3, the component Q is multiplied by the oscillation signal after 90° phase shift which is outputted from a 90° phase converter 7 in the mixer 4. The output signal of an adder 8 is subtracted by the output signal corresponding to the output oscillation signal of an ATT 23 in a subtracter 9, and further the output signal is subtracted by the output signal corresponding to the output oscillation signal of an ATT 25 in a subtracter 10. Namely, this transmitter is operated so as to cancel the DC component that is, a carrier wave leakage component by the output signals of the ATT 23 and 25 in these subtracters 9 and 10.