To achieve excellent working efficiency in installing an anchor, to enable the installation while a shaft part such as a bolt and a reinforcing bar is directly projected from the surface of a skeleton after the installation, and to allow an installation condition to be examined easily, allowing check work after the installation to be performed efficiently.

An anchor 1 includes an anchor bolt 2, a spreading sleeve 3, and a cone nut 4. In the anchor bolt 2, a shaft part 6 thereof includes a thick shaft part 6a connected to a bolt head 5 and a thin shaft part 6b provided on the tip portion side of the thick shaft part 6a, coaxial with the thick shaft part 6a, and having a diameter smaller than that of the thick shaft part 6a, a step 7 is provided between the thick shaft part 6a and the thin shaft part 6b, a male thread 11 to be screwed with the cone nut 4 is formed in the thin shaft part 6b, and a rupture portion 8 with a reduced diameter is formed at a position spaced by a predetermined length from the step 7 of the thick shaft part 6a and ruptures if torque of a predetermined value or more acts on the bolt head 5.