A hook portion is formed to project from a columnar portion of a cover forming a needle cover body. The hook portion is hooked by a stopper wall of an outer cylinder, whereby the needle cover body is inhibited from slipping out of the outer cylinder. An inner cylinder biased toward a barrel by a spring member is accommodated inside the outer cylinder, that is, in a through hole. The needle cover body is provided continuously to the inner cylinder. In addition, the inner cylinder is held inside the outer cylinder as a cam projection is movably engaged with a guide passage formed in the outer cylinder.
