Image forming apparatus

An image forming apparatus comprising:

• a belt on which images of a plurality of colors are formed to be laid on each other by a plurality of image formers that form the images of color components different from each other, the belt being colorless and transparent and having a transparency;
• a plurality of color information detectors that are arranged on a front surface side and a back surface side of the belt, and detect, from the front surface side and the back surface side, color information about a pattern image including two layers formed on the belt by two image formers among the plurality of image formers;
• a hardware processor that calculates a color correction amount of an image formed by the two image formers based on detection results by the color information detectors;
• and
• a storage in which reference color information on two colors forming the pattern image including the two layers is stored, wherein
• when a predetermined timing comes, the hardware processor controls the two image formers to form the pattern image including the two layers on the belt and controls the color information detectors to detect the color information on the two colors on the front surface side and the back surface side of the belt, and
• the hardware processor calculates the color correction amount based on comparison between the reference color information on the two colors stored in the storage and the detected color information on the two colors.