Provided is a very safe pre-filled syringe that reduces the time and efforts required in administering the injection. In the pre-filled syringe, a needle unit (1) attached to a vial includes: a substantially columnar retaining member (10) with needles at both ends a holder member (11) holding the retaining member (10) with three pillar-shaped parts (111) and a holder member (12) holding the retaining member (10) with three pillar-shaped parts (121) and having an attachment portion (125) for the vial. The needle unit (1) is axially retractable when the pillar-shaped parts (111, 121) are alternately arranged in the circumferential direction, and is not axially retractable when distal end surfaces of the pillar-shaped parts (111) in one holder member face distal end surfaces of the pillar-shaped parts (121) in the other holder member. Axially retracting the needle unit (1) makes an injection needle (100A) project, and makes a perforation needle (100B) project inside the vial.
