To provide an image reading apparatus enabling a long light source inside the image reading apparatus to be uniformly cooled in the main scanning direction with a simplified structure without increasing the number of components of the apparatus. An image reading apparatus having an optical reader section that has a long light source along the main scanning direction to read an original, a first holding section that holds the light source, a second holding section adjacent to the first holding section on the side surface side in the sub-scanning direction orthogonal to the main scanning direction of the first holding section, and a partition disposed between the first holding section and the second holding section, where in the partition are formed a first ventilating opening comprised of one or more openings for air inside the first holding section to move to the inside of the second holing section, and second ventilating openings comprised of a plurality of openings provided in the main scanning direction for the air inside the second holding section to move to the inside of the first holding section.