An image reading apparatus includes a light source, a light receiving unit, and an optical system. The light receiving unit includes a plurality of light receiving elements. The optical system includes a plurality of optical components for splitting the light reflected from the object to be read, and guiding the split light to each of the plurality of light receiving elements. The plurality of optical components include a splitting component that splits the light reflected from the object to be read in a direction corresponding to a main direction, and a common component provided with a common portion. The common portion has an optically acting area causing a common effect on the tight split by the splitting component. A cross sectional shape of the optically acting area orthogonal to a direction corresponding to the main direction is the same shape along the direction corresponding to the main direction.