There is provided a cannula that is capable of controlling itself from easily slipping out from an eyeball when a surgical tool or the like is moved, does not damage the eyeball even when the base of the cannula and the eyeball make contact, and controls a pipe from detaching from the base. The cannula is pierced through the eyeball in ophthalmic operations and includes a metal pipe for piercing through the eyeball A； and a base joined to an end side of the pipe and made of a material having flexibility. Moreover, the center part of an eyeball side end surface of the base should be depressed, and the shape of the contact portion of the base should be changed when the base makes contact with the eyeball.
