An injector includes a hollow needle a main body unit including a needle holding portion that holds the needle and a protection device configured to cover the needle before and after puncturing a puncture target with the needle. The protection device includes: an inner member attached to the needle holding portion and being freely rotatable around an outer periphery of the needle holding portion and an outer member configured to (i) cover an outer side of the needle and the inner member before puncturing, (ii) expose the needle by moving toward a proximal end side relative to the main body unit at a time of puncturing, and (iii) cover a distal end of the needle by moving toward a distal end side relative to the main body unit after puncturing.
