A connector (20) includes an outer tube (210), an inner tube (220) held by the outer tube (210), a fluid channel having a hollow passage and accommodated in the outer tube (210), and a ratchet mechanism (240) that allows rotation of the inner tube (220) in one direction while restricting rotation of the inner tube (220) in the other direction. The inner tube (220) includes an insertion attachment portion which is provided on a proximal end side thereof and with which a distal end side of a drug container is screwed to be attached thereto by insertion. In an insertion attachment state in which the drug container is attached by insertion to the insertion attachment portion, the ratchet mechanism (240) restricts rotation of the inner tube (220) together with the drug container in a screwing direction and allows the inner tube (220) to rotate freely relative to the outer tube (210) together with the drug container in an unscrewing direction opposite to the screwing direction.
