Patent ID: 7434680

Claim:
A belt unit attachable to and detachable from a main body, said belt unit comprising: a first roller rotated by a driving force of a driving source; a second roller having an axis substantially in parallel to an axis of said first roller; an endless belt stretched around said first and second rollers; a first supporting member that supports said first roller; a second supporting member that supports said second roller; a positioning member provided on said first supporting member for positioning said belt unit with respect to said main body; a rotational supporting mechanism that supports said second supporting member with respect to said first supporting member in such a manner that said second supporting member is rotatable relative to said first supporting member; and a parallelism maintaining mechanism comprising: a first shaft holding portion that holds shaft portions or bearing portions of said first roller; and a second shaft holding portion that holds shaft portions or bearing portions of said second roller, said second shaft holding portion being fixed to said first shaft holding portion.