An image forming device includes an image forming unit, a conveying unit, a first image detecting unit, a second image detecting unit, and a controller, wherein the controller includes a detecting unit correcting mode in which the first image detecting unit is corrected by using an image detection result by the second image detecting unit, and in the detecting unit correcting mode, a transfer paper conveying speed at the time of image reading by the second image detecting unit is changed to the transfer paper conveying speed different from a normal transfer paper conveying speed at the time of image formation and the first image detecting unit is corrected based on read results of the same image by the first and second image detecting units.