According to one embodiment, an image forming apparatus includes a plurality of process units, a transferring member, a sensor, and a processor. The plurality of process units include a photosensitive drum, an electric charger which charges the photosensitive drum, an exposing device which includes a plurality of light emitting element rows in a sub-scanning direction configured by the plurality of light emitting elements, and irradiates the photosensitive drum to form a latent image, and a developing device which attaches toner to the latent image to form a toner image. The transferring member receives the toner image from the photosensitive drum. The sensor detects the toner image transferred to the transferring member. The processor calculates a skew deviation amount based on the detection result of the sensor, and controls turning on and off the light emitting element based on a central tendency and the skew deviation amount.