Patent ID: 7577380

Claim:
An image forming apparatus comprising: an apparatus body; and a belt unit detachably attached to said apparatus body, wherein said belt unit includes: a belt having an engaging portion; a belt frame; a belt driving roller that is positioned in an axial direction and supported by said belt frame, the belt driving roller structured to receive said belt, and is rotatably driven to move said belt; a belt driven roller that is supported displaceably in the axial direction by said belt frame, the belt driven roller structured to receive said belt, wherein the belt driven roller includes a belt guide that engages said engaging portion to position said belt in a width direction, and is rotated by the circulating movement of said belt; and a transfer member held by said belt frame, and wherein said apparatus body includes: a driving roller axial positioning portion that positions said belt driving roller in the axial direction; and a driven roller axial positioning portion that positions said belt driven roller in the axial direction.