PURPOSE: To sufficiently match the impedance of respective input terminals at a working frequency band, to minimize conversion loss and to be excellent in universal applicability by connecting a capacitor to an Lo port and an RF port.

CONSTITUTION: On a hermetic sealing 102 having 8 pin terminals 101, a transmission transformer 103 and a bridge type diode 104 are arranged, and to an RF port, a capacitor 105 of 2.5pF is connected. Thus, the conversion loss can be made very small, a ferrite core and a winding are made into the same, only by changing the capacitor, the double balanced mixer to match to respective working frequency bands can be constituted and comes to be the mixer excellent in the universal applicability.