An image reading apparatus includes a plurality of conveyance mechanisms for clamping and conveying a medium, an imaging device for generating an input image in which a medium is imaged, a storage device for storing relative positions of the plurality of conveyance mechanisms with respect to an imaging position of the imaging device, and a processor for dividing the input image into a plurality of regions according to a number of conveyance mechanisms clamping a medium when each pixel in the input image is photographed, based on the relative positions, and setting a reliability level to each divided region in such a way that the reliability level increases as the number of conveyance mechanisms related to each region divided increases, and executing image processing on the input image based on at least a region the reliability level of which is greater than or equal to a threshold value.