US Patent 7577380 Image forming apparatus including a belt unit

A belt driven roller having a belt guide that positions a conveying belt in a width direction is supported in an axial direction relative to a belt frame, and positioned in the axial direction relative to a body casing. This can increases positional accuracy of the conveying belt relative to the body casing in the width direction. The belt driven roller is displaceable in the axial direction relative to the belt frame, and even if the belt driven roller and a belt driving roller are positioned in the axial direction relative to the body casing, dimensional tolerance between the belt driven roller and the belt driving roller reduces or eliminates distortion in the belt frame. This can increase positional accuracy of transfer rollers and results in a more stable image quality.