PURPOSE: To securely tighten a nut without damaging a support body by composing a spring washer to comprise a washer main body having a conical cross section, an outer main body which continuously transfers to an inner main body at a transfer part on a support surface, and the transfer part provided with grooves on an upper surface as well as on adjacent parts to the inner and outer main bodies.

CONSTITUTION: This spring washer comprises an outer washer main body 1, an inner washer main body 2, and a transfer part 3, the main bodies 1, 2 are formed to have a conical cross section, and they are opened toward a support surface of the washer. The transfer part 3 has a smaller cross section than adjacent parts to the main bodies 1, 2, and it forms a groove 4 with the adjacent parts. A conical opening angle of the main body 1 is larger than an opening angle of the inner washer main body 2, the main body 2 surrounds a center opening 5, and a screw, a bolt or the like is inserted from there. The main bodies 1, 2, and the groove 4 are concentrically provided around the center opening 5. In this constitution, the groove 4 acts as a hinge, thereby fixes a nut or the like securely without damaging a support body.