To restore the performance of a mechanical mechanism to be reused to an initial state.

An exposure unit which is reused in recycling is assembled with the film unit with a lens. A shutter driving lever for kicking a shutter blade and a charging spring for generating the kicking force are assembled with the exposure unit. Lubricant for restoring the variation of a shutter opening/closing time in recycling to the initial state is applied on the sliding contact part between the shutter driving lever and the charging spring. After the lubricant is applied, the shutter opening/closing time is measured several times, and then, whether the mechanism can be reused or not is judged based on the measurement results.