An image reading apparatus is provided. The image reading apparatus includes a first transparent section to have a first original sheet set thereon, a second transparent section to have a second original sheet conveyed by a sheet conveyer, a reader unit being movable in a sub-scanning direction to read the image on the original sheet being set on the first transparent section and to be maintained still to read the image being conveyed by the sheet conveyer, a white reference member, of which image is read by the reader unit and recognized as a reference white color, and a light reductive member arranged on an inner bottom of a casing to reduce an amount of incident light.