An image reading apparatus includes a reading unit, an extraction unit and a generation unit. The reading unit outputs reference plate reading information. The extraction unit sets a pixel of the reference plate reading information as a notice pixel and repeatedly extracts one of the notice pixel as a target pixel until the number of the target pixels is more than a predetermined value when a ratio of a pixel value of the notice pixel to an initial value is more than a predetermined range. The generation unit generates correction information by substituting a pixel value of the target pixel with a correction value using the initial value when the extraction unit extracts all pixels of the reference plate reading information, and generates correction information by setting the pixel values of all the pixels as the initial value when the extraction unit does not extract all the pixels.