To provide a push-locking pin for preventing a pin body from being bared, and capable of maximally straightly piercing, by covering a clearance easily generated by a pin body between boards and itself in its pierced-in use state, in the push-stop pin composed of a head part and the pin body.

This bellows spring is formed of the head part 1, the pointed-shaped pin body 2 having integrally the proper length on an under surface of this head part 2, and an expandable elastic body 3 for surrounding the pin body 2 on the under surface of the head part 1. When suspending by piercing this pin body 2 in boards 6 such as a wall and a bulletin board by piercing the pin body 2 in paper such as a memorandum and a poster by pressing the head part 1 by fingers, the clearance with the boards 6 is covered when the surrounded expandable elastic body 3 contracts in response to a piercing-in state. Alternatively, easy falling-off/dropping from the boards and the bulletin board 6 can be prevented by installing a spiral pin body.