The present invention is provided with: an outer cylinder needle base (15) provided to an outer cylinder needle (3)； an inner needle base (7) provided to an inner needle (2) and capable of penetrating into the outer cylinder needle base (15) when the inner needle (2) is inserted in the outer cylinder needle (3)； a lock receiving part (34) provided to the inner needle base (7)； a protruding position locking part (35) capable of locking the lock receiving part (34) in a protruding position and an retraction position locking part (36) capable of locking the lock receiving part (34) in an retraction position, the protruding position locking part (35) and the retraction position locking part (36) being provided to the outer cylinder needle base (15)； an urging member (31) for urging the inner needle (2) in the direction of moving from the protruding position to the retraction position； and an unlocking operation member (37) capable of unlocking the lock receiving part (34) and the protruding position locking part (35)； and when the protruding position locking part (35) and the lock receiving part (34) are unlocked by the unlocking operation member (37), the inner needle (2) is moved from the protruding position to the retraction position by the urging force of the urging member (31), and the lock receiving part (34) is locked by the retraction position locking part (36).
