An outer unit (101) includes a shield (20) that has an inner cavity (24) and a soft outer needle (30) that is fixed to a front end of the shield. An inner unit (102) includes an inner hub (40) that is disposed within the inner cavity of the shield, a hard inner needle (50) that is fixed to a front end of the inner hub, and a tube (60) that is connected to a rear end of the inner hub. The inner unit is displaceable relative to the outer unit from an initial position at which the inner needle penetrates the outer needle and protrudes from a leading end of the outer needle to a retracted position at which the inner needle is housed within the inner cavity of the shield. The inner unit located at the initial position is fastened to the outer unit so that the inner unit is prevented from moving toward the retracted position due to a reaction force that is exerted on the inner needle during insertion with the inner unit being disposed at the initial position.
