A first connector includes a first connector main body configured from an outer tube of cylindrical shape, an inner tube of cylindrical shape, a hub disposed at a proximal end portion of the outer tube, and a clip disposed so as to be removable at the proximal end portion of the outer tube, a hollow needle supported on the hub, a first sealing member supported on the inner tube, a coil spring serving as puncturing portion biasing means for biasing the first sealing member toward the distal direction, and a clamping member disposed upon the outer tube. In a state in which the clip is mounted to the proximal end portion of the outer tube, a protrusion of the clip engages with a protrusion of the hub, and thereby rotation of the hub is prevented. If the clip is removed, the hub becomes rotatable with respect to the outer tube.