The frequency conversion circuit 30 as an element of a radio communication device, the frequency conversion circuit for converting by using a local oscillator 32 the frequency of a signal which is modulated with a reference oscillation signal from a reference oscillator 31. The frequency conversion circuit 30 is provided with a first mixer 36, a change-over switch 35, and a second mixer 33. The first mixer 36 mixes the reference oscillation signal from the reference oscillator 31 and a local oscillation signal from the local oscillator. The change-over switch 35 selects one of a mixed signal from the first mixer 36 and the local oscillation signal from the local oscillator 32. The second mixer 33 mixes the signal modulated with the reference oscillation signal with an output from the change-over switch 35. The frequency conversion circuit 30, thus configured, may widen a frequency range, without an additional local oscillator, guaranteeing signal purity and response time for shifting the oscillation frequency.