PURPOSE: To fit the AF unit to a camera main body without placing the load such as twist on the AF unit by providing a frame body with a ring-shaped part, inserting a lens barrel into the ring-shaped body and supporting the lens barrel, and providing a rotation stop mechanism.

CONSTITUTION: A light emission part 26 and a light reception part 28 are arranged on the frame body 23 of the AF unit 22 at a specific distance to each other, the ring-shaped part 24 is formed at the center part of the frame body 23, and a lock lever 30 is projected and formed at its side part. Then the lens barrel 20 of a photographic lens is inserted in to the ring-shaped part to support the unit 22, a pin 34 is inserted into the lock hole 32 of the lever 30 and stopped from rotating, and the pin is prevented by a C ring from falling. Consequently, the unit 22 can be fitted to the camera main body without using any screw, so the position relation between the light emission part 6 and light reception part 28 never changes.