To provide a fastener capable of securing rigidity of a fastening part and preventing breakage of a member when excessive loads act thereon.

The fastener for fastening a support member such as a foundation plate 42 and a connection member such as a column 51 includes a bearing body 11a, a buffer body 38a and a mooring tool 55 and so on. The bearing body 11a is arranged at the center inside a space S where the support member and the connection member face each other, and includes a base plate 12 to be in surface contact with the support member, a loading plate 14 to be in surface contact with the connection member, and a connection part for connecting both plates. The buffer body 38a uses a U-shaped leaf spring or the like, is arranged at an outer edge inside the space S where the support member and the connection member face each other, and generates reaction force corresponding to the displacement of the connection member or the like. When the connection member or the like is lumber, the mooring tool 55 is buried in it and mitigates concentrated loads acting on the lumber. The fastener by this invention surely transmits compression loads or the like by the bearing body 11a, and in an earthquake or the like, absorbs energy by the buffer body 38a and prevents the breakage of members.