There is provide a technique which can contribute to reduction of data capacity of image data read from an original document in an image reading apparatus, and can contribute to realization of a flexible image processing to meet user's requests. There are included a first image reading unit to read an image in monochrome from an original document at a first resolution, a second image reading unit to read an image in color from an original document at a second resolution lower than the first resolution, a position information acquisition unit to acquire position information indicating, in respective image data read by the first and the second image reading units from the same original document, corresponding positions of respective pixels on the original document, a color information acquisition unit to acquire color information indicating colors of the respective pixels in the respective image data, and a storage unit to associate the position information acquired by the position information acquisition unit with the color information acquired by the color information acquisition unit with respect to the pixel corresponding to the position information and to store them in a specified storage area.