PURPOSE: To hold a lens cap at the side face of a lens cylinder part simply and easily by opposing the permanent magnet of the lens cap to the permanent magnet of the side face of the lens cylinder part by a rotation, and constructing the both permanent magnets so as to attract each other.

CONSTITUTION: When photographing by a photographing camera 2, a lens cap 6 is detached from the end of a lens cylinder part 4, as well as the lens cap attaching part of a rotation mechanism 16 is rotated in a side face direction of the lens cylinder part 4. In accordance with this rotation, the lens cap 6 attached to this attaching part is also rotated to the side face side of the lens cylinder part 4. As the result of the rotation, since the respective prescribed positions of the lens cap 6 and the lens cylinder part 4 are opposed each other, permanent magnets 18 and 20 at the both prescribed positions are absorbed each other, and as the result, the lens cap 6 is held at the lens cylinder part 4. Thus, it is possible to hold the lens cap 6 at the side face of the lens cylinder part 4 simply and easily.