A noise reduction unit includes a conductor having a winding portion and a ring-shaped core which is made of a magnetic material and is inserted through the winding portion, and a housing which housesthe conductor and the ring-shaped core. An inner wall surface of the housing is formed with a recess configured to receive a part of the winding portion located on an outer circumferential surface ofthe ring-shaped core. The conductor is housed in the housing so that the part of the winding portion is received in the recess.