1. A position deviation order detection method for detecting, in order to determine a streak unevenness correction chart that has a size corresponding to the size of a position deviation of an image generated when the image printed by an inkjet printer is read using a scanner and includes a density image pattern formed by a plurality of units for correcting the position deviation of the image, the size of the position deviation of the image, the method comprising: calculating a difference between input image data of an original image used for printing the image by the inkjet printer and output image data obtained by reading the image using the scanner for each pixel; comparing the calculated difference with a first threshold value and extracting pixels for which the difference is equal to or larger than the first threshold value; and detecting the size of the position deviation of the image according to the number of pixels of a pixel group that forms a closed figure among the extracted pixels.