An image processing apparatus, includes: an acceptance unit that accepts image data and reading data read from a medium; an extraction unit that extracts a rectangular image by segmenting one image of the image data and the reading data to have a size calculated based on an error; a searching unit that searches for a matching position of a rectangular image in the other image of the image data and the reading data, which corresponds to a position of the rectangular image extracted by the extraction unit within a range of a movement amount calculated based on the size of the rectangular image extracted by the extraction unit and a predetermined size calculated by the error; and a comparison unit that compares the rectangular image extracted by the extraction unit with the rectangular image in the other image at the position searched by the searching unit.