PURPOSE: To provide a mounting apparatus with high strength at low cost by forming a locking hole part from a different material having higher strength than a material for a mounting part, said locking hole part is formed in the mounting part to lock at the time of joining.

CONSTITUTION: A mounting part 1 in the lens-barrel side of an exchange lens is made of a metal and a locking hole part 3 to lock the mounting part 1 after the mounting part 1 is attached to a mounting part in the camera main body side is formed in the mounting part 1. The locking hole part 3 is made of a material with high strength, for exmaple, nickel-chromium steel, high carbon steel, which is like a tool steel produced by heat treatment, e.g. hardening, to heighten the hardness and the part 3 is set by pressure in an installation hole 1c of the mounting part 1. A long hole 3a formed in the locking hole part 3 is made to have a small oval shape longer in the radiate direction from an optical axis of a lens as a center and absorbs the eccentricity by fitting backlash degree attributed to manufacturing error. Consequently, even if high pressure is applied to a camera main body through a locking pin of the mounting part, rotary backlash scarcely occurs.