An image reading apparatus is provided with a carriage accommodating an optical unit for image reading, a driving member for moving the carriage, a guide rail, a guide-rail engaging portion engaged with the guide rail, a holding portion for holding the driving member, a guide plate and a claw portion. The claw portion presses the guide-rail engaging portion against the guide rail by partially deforming the driving member to produce a tensile force in the driving member and causing the tensile force to act on the first end portion of the carriage, and produces such a rotation moment for biasing the first end portion of the carriage in a first direction parallel with a sub scanning direction and, on the other hand, biasing the second end portion of the carriage in a second direction opposite to the first direction and parallel with the sub scanning direction.