Image forming apparatus, image bearing member life detecting method, and process cartridge detachably attachable to image forming apparatus

An image bearing member life detecting method capable of accurately detecting that the life of an image bearing member has expired or will expire soon, an image forming apparatus using the method, and a cartridge detachably attachable to the image forming apparatus, are provided. An image bearing member damage index number D representing the consumption degree of an image bearing member is calculated on the basis of an applying period under each condition of an electrostatic charge bias applied to an electrostatic charging portion for forming an electrostatic latent image on the image bearing member, and/or the contact period of a developing portion for developing the electrostatic latent image on the image bearing member. When the process speed is switched, the calculation method is switched in accordance with the process speed, and the image bearing member damage index number D is calculated. The image bearing member damage index number D is integrated and stored as an image bearing member damage integration value S. The image bearing member damage integration value S is compared with life information R corresponding to the image bearing member damage integration value S for a predetermined life of the image bearing member, thereby detecting the life of the image bearing member.