A seal washer of the present invention includes a metal washer body including a center hole, an outer resilient material projecting from an outer periphery of the washer body to a location lower than a lower surface of the washer body, and an inner resilient material provided on an inner periphery of the washer body which faces the center hole. If a fastening force in an axial direction is applied, since the lower surface of the washer body metal-touches on a mating member, loosening does not occur unlike a conventional technique. In addition, since no further compression load is applied to the resilient material, a phenomenon that the resilient material is deformed in a crushed manner does not occur.