To prevent deterioration in the amplitude error by correcting an isolation characteristic of the balanced modulator, through the application of an offset voltage.

In the balanced modulator for a microwave band, provided with two diodes 2, 3 and a line pattern in matching with the frequency band, capacitive stubs 10, 11 and 12, 13, each consisting of one or more element are provided just aside lines 4, 5 extending from a balance-unbalance conversion section 1 to be mounted with the diodes 2, 3 at an interval of λ/8, and the capacitive stubs 10, 11 and 12, 13 and the lines 4, 5 are adjusted by connecting them with bonding wires.