An image forming apparatus includes an image carrier, a developing device, a control unit, and a density measuring unit. An electrostatic latent image is formed on the surface of an image carrier. A developing device supplies toner to the image carrier and develops the electrostatic latent image formed on the image carrier to form a toner image. The density measuring unit measures the toner density of the plurality of first patch toner images formed by the developing device. The control unit calculates a relationship between the toner density of the plurality of first patch toner images measured by the density measuring unit and the applied voltage applied to the developing device when the plurality of first patch toner images are formed, and adjusts the applied voltage based on a calculation result.