An image forming apparatus of the invention includes an image carrier, an exposure device performing exposure for forming a toner image on a surface of the image carrier and having at least a first exposure light source and a second exposure light source, a sensor for detecting specified patterns, which are formed on the image carrier at a specified time with use of the first and second exposure light sources, a storing unit for storing a correlation, which is attained from a detection result by the sensor, between the first and second exposure light sources, and a controller for controlling the first and second exposure light sources based on the correlation.