A microwave heating device mountable to an electric device, includes: a commercial power supply; an AC/DC converter which outputs a plurality of DC voltages according to power supplied from the commercial power supply; a controller which receives power from the AC/DC converter and totally controls the electric device; a microwave processing device using a compound semiconductor which receives a plurality of outputs of the AC/DC converter and outputs a microwave; and a plurality of loads connected between, of the DC voltages output from the AC/DC converter, a predetermined Vd voltage and ground through a plurality of contacts. The loads form a group of electric components in the electric device. The controller controls power supply to the loads, and controls on/off of the contacts to drive the loads by the Vd voltage regardless of the voltage of the commercial power supply.