A medical needle includes a needle body including a needle tip on a front end of the needle body; a shaft provided on a base end of the needle body; a housing pipe including a first tube, and a second tube; and a lock member that includes at least one engaging unit that is releasably engaged with the shaft, and at least one engagement release unit. The shaft is slidable from a first position at which the front end of the needle body protrudes from the housing pipe by a predetermined length, to a second position at which the front end of the needle body is located in the housing pipe. Engagement of the at least one engaging unit with the shaft is releasable by pressing the at least one engagement release unit inward.