An on-board electric compressor that comprises: a housing; a compression unit; an electric motor; and an inverter device. The inverter device comprises: an inverter circuit that converts direct current power to alternating current power; and a noise reduction unit that is provided on an input side of the inverter circuit and that reduces common mode noise and normal mode noise that are included in the direct current power. The noise reduction unit comprises: a common mode choke coil; and a smoothing capacitor that, in cooperation with the common mode choke coil, constitutes a low pass filter circuit. The common mode choke coil has: a core that has a first core part and a second core part; a first winding that is wound around the first core part; and a second winding that is wound around the second core part.