An image forming apparatus which adjusts toner density in a developing device according to humidity. However, an image quality may decrease if the humidity changes between the time when a power source is turned off and the time when the power source is turned on. Accordingly, the image forming apparatus includes an absolute humidity calculator and a toner density controller for changing the toner density in the developing device in accordance with a difference between the absolute humidities. A storage controller controls the storing of an absolute humidity in a storage portion; and a toner removal controller controls the removal of residual toner particles from the developing device if a difference between an absolute humidity detected by the humidity detector when the power source is turned on and an absolute humidity stored in the storage portion is more than a predetermined value.