A plug for a vehicle includes: a body portion; a plurality of insertion portions configured to be inserted into a through-hole provided in a housing; and a flange portion having a notch formed on an outer periphery so as to restrict a rotation of the body portion around an axial center. The insertion portions are formed at two positions opposed to each other across a straight line passing through the notch and the axial center and are provided with retaining lugs engageable with the through-hole.