Disclosed is a catheter which can protect an operator and a person being operated on from the risk of a pierced wound by a needle when the needle is discarded after used. As an example, disclosed is a catheter comprising: a needle； a plug, the front end of which is coupled to the needle； a first case formed to surround the needle； a socket coupled to the front end of the first case； a gear which vertically fastens the first case and the socket, includes a sawtooth formed on one side of the outer periphery thereof, and has a needle groove formed therein and penetrated by the needle； a catheter hub fastened by the sawtooth of the gear； and a tube coupled to the front end of the catheter hub.
