To easily improve isolation between a high frequency signal and a local oscillation signal with a simple circuit configuration at a low cost.

In this mixer circuit, a high frequency signal RF passing through a 1st band pass filter BPF 11 and a filtered local oscillation signal LO passing through a 2nd BPF 13 pass through a Wilkinson distributor 12 and an impedance matching circuit 14 and enter a frequency converter 15. The constants of components of the Wilkinson distributor 12 are selected so that each impedance obtained by viewing the side of the filtered high frequency signal RF from an input terminal A of the Wilkinson distributor 12, viewing the side of the filtered local oscillation signal LO from an input terminal B, viewing the side of the frequency converter 15 from an output terminal D respectively and each impedance obtained by viewing the Wilkinson distributor 12 from the input terminal A, the input terminal B and the output terminal D respectively are matched and the isolation between the filtered high frequency signal RF and the filtered local oscillation signal LO is maximized.