An image reading device includes a document mounting plate having a mounting surface and a rear surface, and an image reading unit. The image reading unit includes a photoelectric converter facing the rear surface, a case to hold the photoelectric converter, and at least one first rotating member and at least one second rotating member that rotate and receive a pressing force from the rear surface of the document mounting plate as the image reading unit moves. The image reading unit also includes a holder configured to support the case and at least one urging device positioned between the holder and the case. The at least one urging device urges the case toward the rear surface, and exerts an urging force opposite to the pressing force, and balances against the pressing force.