An image forming apparatus includes a charge unit, an exposure unit, an exposure voltage detector, a development unit, and a concentration detector. The exposure voltage detector detects a potential of latent image formed as a test pattern on an image carrier. The concentration detector detects concentration of developed test pattern. The image forming apparatus further includes an exposure power controller, an exposure ratio controller, a charging voltage controller, a development bias voltage controller, and an image forming condition adjustment controller. A suitable image forming condition is computed using test patterns formed by changing combinations of charging voltage, exposure power, and exposure duty. The charging voltage is changed in two levels or more. The exposure power is changed in three levels or more. The exposure duty per unit area is changed in two levels or more.