An image forming apparatus is equipped with a process cartridge detachable therefrom, where the process cartridge includes an element relating to image formation. A drive time of the process cartridge driven in the image forming apparatus is counted and it is judged whether an accumulation of the drive time counted reaches a predetermined value. When it is judged that the accumulation of the drive time reaches a predetermined value, an image forming condition of the image forming apparatus is changed over at a timing when the image forming apparatus does not conduct image formation.