An image forming apparatus includes an image reader unit and a control unit. The image reader unit generates read data. The control unit generates output data of image data cropped from the read data. When cropping a plurality of image data, the control unit sets one side of the read data to a first reference side and sets another side perpendicular to the first reference side to a second reference side, and for each of the plurality of image data, the control unit detects a first distance between the first reference side and the image data in a direction parallel to the second reference side, and a second distance between the second reference side and the image data in a direction parallel to the first reference side, and sets an output order of the plurality of image data based on the first distances and the second distances.