The syringe (10) includes first and second outer cylinders (14, 16) having a flowing port 26 which allows liquid to flow therethrough at a distal end, and a plunger (22) inserted from the proximal side of the outer cylinder (14, 16). The syringe (10) includes a tooth portion (90) provided along the direction of movement of the plunger (22), and a hook (98) configured to lock the tooth portion (90) at a predetermined locking position and prevent the movement of the plunger (22) in the direction toward the proximal end. The hook (98) retracts from the locking position in association with the unlocking operation and restores automatically to the locking position after the unlocking operation.
