Microwave two-phase modulator and mixer each comprising a balance/unbalance transformer section to which a microwave signal is applied; a synthetic/branching line section which is connected to the both ends of the balancing line of the balance/unbalance transformer section on the balancing line side; isolation diodes are mounted between diode-mounting lines section and fan-shaped patterns; a plurality of modulating characteristic-adjusting, capacitive stubs placed near the diode-mounting lines; an input line; a modulating signal input line; and a modulated signal output line. The modulating characteristics are adjusted by connecting the diode-mounting lines and the plurality of capacitive stubs by bonding wires or cutting some of the connecting wires.