An image reading device, which is included in an image forming apparatus, includes a first transparent body, a second transparent body, a holding body, and a reading body. The second transparent body is disposed separated from and inclined at a predetermined angle to the first transparent body. The holding body holds the first and second transparent bodies. The reading body moves in a sub-scanning direction along the first and second transparent bodies. The holding body includes a flat face and a frame-shaped face. The flat face is contiguous to the first transparent body on a same plane and smoothly connected with the second transparent body. The frame-shaped face projects outwardly beyond the second transparent body facing the reading body. The reading body moves and contacts the first transparent body and the holding body, and moves with a gap relative to the second transparent body.