A lens attaching/detaching device includes a lever holding plate that has an elastic piece which presses a lock releasing lever in a direction away from a locking mechanism and holds the lock releasing lever while the lock releasing lever is guided by a lower case. The lock releasing lever includes a first sliding part and a second sliding part which are guided by the lower case. The first sliding part and the second sliding part are arranged at different positions in a Z direction and an X direction orthogonal to a Y direction. An operation part is disposed at the same position as that of the first sliding part in the Z direction. An actuation part is disposed at the same position as that of the second sliding part in the Z direction. The lower case includes a first guiding part which guides the first sliding part and the second guiding part which guides the second sliding part.