A fastener to fasten a member to be fastened includes a shaft portion, a tool working surface, and an external operation restricting portion. The shaft portion is provided with a male thread configured to be rotated about an axis line to work so as to fasten the member to be fastened. The tool working surface is formed to a tool working portion integrated with the shaft portion. A tool to rotate the shaft portion works to the tool working surface. The external operation restricting portion is configured to restrict the rotation of the shaft portion through an operation from outside the fastener. In this fastener, the tool working surface to which the tool works is formed in an approximately cylindrical inner surface shape.