An image forming apparatus includes an image supporting member; an exposure device for forming a static latent image on the image supporting member; a developing device for developing the static latent image formed on the image supporting member; an image control unit for controlling a condition for forming an image; and a density sensor for detecting a developer density. In the image forming apparatus, a first pattern for detecting the developer density is formed to determine whether the developer density is proper. When the developer density thus detected is greater than a threshold value, a second pattern for discarding developer is formed to discard the developer. A third pattern for density correction is formed to perform the density correction.