An image forming apparatus includes an apparatus main body, a photoreceptor drum, a charging apparatus, an exposure apparatus, a developing device, a charging bias applying unit, a developing bias applying unit, an image condition adjusting unit, and a print density measurement unit. The image condition adjusting unit forms a second electric potential region by applying the charging bias where a first differential electric potential is subtracted from a first tentative charging bias on a circumference surface of a photoreceptor drum, and forms a second toner image by an electric potential difference between the second electric potential region and a developing roller by applying the target electric potential. The image condition adjusting unit decides value of the charging bias corresponding to the target electric potential from measurement results of print densities of a first toner image and the second toner image measured by the print density measurement unit.