In an image reading apparatus, the linear coefficients of expansion of conveyance drive rollers and a linear coefficient of expansion of the holding unit are determined such that the amount of change in the outer diameter of each of the conveyance drive rollers due to a change in temperature environment is substantially the same as the amount of change in the interval between the first reading unit and the second reading unit due to a change in the temperature environment. The conveyance drive rollers are attached to a rotary shaft such that the positions of head portions of screws are alternately located along the axis direction of the rotary shaft on opposite sides of the outer circumference surface in a direction perpendicular to the axis direction of the rotary shaft.