For supporting a cylindrical photosensitive drum, a high-precision high-strength supporting apparatus is disclosed to include a sleeve member and a shaft member. The sleeve member has an outer wall for attaching to the photosensitive drum, an inner wall within which an axial hole is defined, a first retaining portion positioned at the inner wall, and four locating ribs disposed inside the axial hole. The shaft member has an outer tube inserted into the axial hole of the sleeve member, a second retaining portion provided on the outer tube and engaged with the first retaining portion of the sleeve member, a connecting portion inwardly extending from the outer tube, an inner tube disposed at an inner end of the connecting portion, and four locating slot provided on the inner tube and engaged with the locating rib of the sleeve member.