A noise filter disclosed herein is configured to suppress a common mode voltage that is generated in cables connected to an electric power converter. The noise filter includes: detecting capacitors connected to the cables, respectively, and configured to detect the common mode voltage; an operational amplifier having a positive input terminal via which the common mode voltage detected by the detecting capacitors is inputted; an emitter follower circuit having an input terminal connected to an output terminal of the operational amplifier and having an output terminal connected to a negative input terminal of the operational amplifier; and a transformer configured to apply a compensating voltage to each of the cables by applying a voltage at the output terminal of the emitter follower circuit to each of the cables in opposite phase.