To provide a washer comprising two inner and outer annular bodies that are coaxially juxtaposed to each other and to make it possible to hold a mutually nonturning state and besides for one annular body to be displaced in its axial direction in relation to the annular other body.

In the washer, the inner and outer two annular bodies coaxially juxtaposed to each other constitute a flat annular body. There are provided a first movably supporting surface for moving in concert with a nut and a second movably supporting surface for moving in concert with an object to be fastened at one end and the other end of the axial direction of the flat annular body, respectively. Further, there is provided a rotation resistance surface for moving in concert with a thread portion of a bolt at an inner circumferential surface of an inside annular portion. When the nut is rotated to rotate the bolt, the nut engages with the thread portion of the bolt to prevent rotation of the bolt, thereby generating pulling force for pulling the bolt in the axial direction in the nut. As a result, only when the pulling force exceeds a certain limit, the inside annular portion can slide in the axial direction in relation to an outer annular portion.