PURPOSE: To dispense with any inclined washer by furnishing a spherical part on a plate-shaped washer, forming a long hole along the spherical surface, and providing stepless adjustability for the fastening angle of a nut to be screwed on an anchor bolt which is mounted on the slope face concerned.

CONSTITUTION: A spherical surface part 2 is formed in the center of the body 1 of a washer, and a long hole (bolt hole) is formed along the spherical surface. When this washer 1 is used in an anchor to be mounted for protection of a slope face, the bottom surface of the washer 1 is put alongside the slope face in the case where any angle exists between the anchor and slope face, and thereby the nut fastening angle is made adjustable steplessly. The washer is thus given an angle adjusting function, and it is no more needed to use any inclined washer to be prepared separately. This simplifies execution of works and enhances the economy.