An object is to provide a noise filter that can achieve high reliability. A noise filter (10) includes: a noise detection unit (12) which detects a common mode noise (CN) flowing through an electric path (11); an amplification unit (16) which, on the basis of the common mode noise (CN) detected by the noise detection unit (12), generates a cancellation signal (CS) for canceling out the common mode noise (CN); an injection unit (14) which injects the cancellation signal (CS) into the electric path (11); an abnormality detection unit (17) which detects abnormality of the noise filter (10) on the basis of output voltage or output current of the cancellation signal (CS), and outputs an abnormality detection signal (AS); and a protection circuit (18) which inhibits an abnormal cancellation signal (CS) from being injected into the electric path (11), on the basis of the abnormality detection signal (AS).