A compensation signal generator generates a compensation signal for canceling an electromagnetic noise on a connection line on the basis of a detection signal of a noise detector. A compensation signal injector injects the compensation signal into the connection line. A compensation signal detector outputs a detection signal of the compensation signal. A low-frequency component subtraction unit amplifies a component in a predetermined first frequency region of the detection signal and negatively feeds back the amplified component to the compensation signal generator. An intermediate frequency component addition unit positively feeds back a component of a predetermined second frequency that is higher than the first frequency region in the detection signal to the compensation signal generator.