A frequency converter includes a first pair of transistors including first and second transistors, a second pair of transistors including third and fourth transistors, and a variable impedance circuit. The first transistor includes source terminal being connected to positive-phase input terminal, drain terminal being connected to positive-phase output terminal, and gate terminal being supplied with positive-phase local signal. The second transistor includes source terminal being connected to positive-phase input terminal, drain terminal being connected to negative-phase output terminal, and gate terminal being supplied with negative-phase local signal. The third transistor includes source terminal being connected to negative-phase input terminal, drain terminal being connected to positive-phase output terminal, and gate terminal being supplied with negative-phase local signal. The fourth transistor includes source terminal being connected to negative-phase input terminal, drain terminal being connected to negative-phase output terminal, and gate terminal being supplied with positive-phase local signal.