An image forming apparatus (100) includes an electrostatic latent image bearer (2Y); a charger (3Y) to charge a surface of the electrostatic latent image bearer (2Y); a power source (50Y) to output a charging bias supplied to the charger (3Y); an electrostatic latent image writing unit (6) to write an electrostatic latent image on the surface of the electrostatic latent image bearer (2Y) charged by the charger (3Y); a developing unit (4Y) including a developing member (4aY) to develop the electrostatic latent image to obtain a toner image; a developing power source (5 1 Y) to output a developing bias supplied to the developing unit (4Y); a processor (30) to adjust the charging bias output from the power source (50Y) to a predetermined target value; and a storage unit (30c) to store an adjustment value algorithm.
