To remarkably reduce an adjacent channel leakage signal included in a transmission signal, by improving phase noise performance of a local oscillator.

A data signal generator circuit 11 outputs a digital data signal in which a center frequency is changed according to a channel selection control signal. A local oscillator 20A outputs a LO signal in a frequency bandwidth of n-multiple of a channel frequency interval of an RF signal, and includes switchover means for switching an upper-side frequency and a lower-side frequency by mixing an IF signal with the LO signal, as an RF signal output from an orthogonal mixer circuit. When the radio frequency RF falls to or exceeds a center frequency of an RF filter, there is provided control means for setting a local frequency LO1/LO2 to have a smaller/larger value than the lower/upper limit of the bandwidth of the RF filter, and for controlling the switchover means in a manner to make the orthogonal mixer circuit output an upper-/lower-side frequency.