An imaging apparatus has in a first cam groove a first cam surface whose lead is lying with respect to the rotating direction of a drive ring, and a second cam surface whose lead is steep with respect to the rotating direction of the drive ring, and when transition is effected from an accommodated state to a use state, a follower member passes the first cam surface, and when transition is effected from the state where the follower member is engaged with a second cam groove to the accommodated state, the follower member passes the second cam surface.