A connector is connectable to a medical device that includes a female connector portion. The connector includes: a main body member including: a cylinder portion that is insertable into the female connector portion, and a lock portion configured to, upon insertion of the cylinder portion into the female connector portion, pass over part of the medical device and then move in a predetermined locking direction to lock the medical device; and a lock member that is movable with respect to the main body member. When the main body member is in a state in which the lock portion locks the medical device, the lock member is moveable to a lock position at which the lock member limits movement of the lock portion in a predetermined unlocking direction.