PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of highly precisely superposing a toner image on an intermediate transfer body by reading an electrostatic image scale, which is constituted by aligning narrow electrostatic image lines, with a potential sensor.SOLUTION: A drum scale reading sensor 34b detects an electrostatic image scale 31b written on the outside of a developing area of a toner image using an exposure device 16b. A belt scale reading sensor 33b detects an electrostatic image scale 32 written on the outside of the developing area of a photosensitive drum 12a and transferred to an electrostatic image recording track 25. A control section 48 controls a drum drive motor 6a to position the electrostatic image scale 31b at the electrostatic image scale 32. Thereby, the toner image of the photosensitive drum 12b is highly precisely superposed on a yellow toner image, which is transferred from the photosensitive drum 12a to an intermediate transfer belt 24, and transferred to the intermediate transfer belt 24.