An image forming apparatus comprising: an image forming section that forms an image on an object; a controlling section configured to control the image forming section to form a calibration pattern on the object, the calibration pattern including a plurality of marks in a first group and a plurality of marks in a second group, the plurality of marks in each of the first group and the second group being arranged in a first direction over a predetermined range, characterized by the plurality of marks in each of the first group and the second group including first marks and second marks, the first marks having rectangular shapes, and the second marks having elongated parallelogram shapes that are slanted with respect to a second direction different from the first direction, the second marks including at least a pair of single-color marks slanted with respect to the second direction in opposite directions to each other, the first mark in the first group and the second mark in the second group being formed at the same position in the second direction in at least part of the predetermined range, the first mark in the second group and the second mark in the first group being formed at the same position in the second direction in at least part of the predetermined range; a detecting section configured to detect the first mark and the second mark formed on the object; and a correcting section configured to correct, based on the detected first mark, a deviation in the first direction of an image forming position at which the image forming section forms an image, and corrects, based on the detected second mark, a deviation in the second direction of the image forming position. an image forming section that forms an image on an object; a controlling section configured to control the image forming section to form a calibration pattern on the object, the calibration pattern including a plurality of marks in a first group and a plurality of marks in a second group, the plurality of marks in each of the first group and the second group being arranged in a first direction over a predetermined range, characterized by the plurality of marks in each of the first group and the second group including first marks and second marks, the first marks having rectangular shapes, and the second marks having elongated parallelogram shapes that are slanted with respect to a second direction different from the first direction, the second marks including at least a pair of single-color marks slanted with respect to the second direction in opposite directions to each other, the first mark in the first group and the second mark in the second group being formed at the same position in the second direction in at least part of the predetermined range, the first mark in the second group and the second mark in the first group being formed at the same position in the second direction in at least part of the predetermined range; a detecting section configured to detect the first mark and the second mark formed on the object; and a correcting section configured to correct, based on the detected first mark, a deviation in the first direction of an image forming position at which the image forming section forms an image, and corrects, based on the detected second mark, a deviation in the second direction of the image forming position.