An on-vehicle motor-driven compressor includes a compression unit, an electric motor, and an inverter device. The inverter device includes an inverter circuit and a noise reducer. The noise reducer includes a common-mode choke coil and a smoothing capacitor. The common-mode choke coil includes a case, a loop-shaped core accommodated in the case, a first winding and a second winding that are wound around the case, and a loop-shaped conductor that covers the core and the case. Parts of the conductor that are opposed to each other between the first winding and the second winding are spaced apart from each other. The case includes two projections that project from an outer surface of the case. The conductor is held by the two projections such that the conductor is spaced apart from the first winding and the second winding.