A hub (40) can be displaced between an initial position at which the hub is located on a front end side of an inner cavity of a shield (20) and an inner needle (50) penetrates an outer needle (30) and a retracted position at which the hub is located on a rear end side of the inner cavity of the shield and the inner needle is housed within the inner cavity of the shield. A stopper (170) includes an insertion portion (172) that is inserted into the inner cavity of the shield and a base portion (180) that is located on a rear end of the insertion portion. The base portion includes a roof portion (183) that exposes part of an outer circumferential face of a tube (60) connected to the hub and covers the remainder thereof, and a pair of grasping portions (185) that are arranged to sandwich the tube and can be elastically displaced so as to grip the tube. Accordingly, the possibility of an operational error is reduced in which the operator pulls out only the stopper after the puncture and forgets to house the inner needle within the shield. Furthermore, the need for changing the grip position between when performing puncture and when housing the inner needle within the shield is reduced.