An image forming apparatus comprising: an image bearing member capable of carrying an electrostatic image; a developing device configured to develop an electrostatic image formed on said image bearing member into a toner image, using a developer including toner and carrier; an exchangeable supply container configured to supply the developer into said developing device; a content sensor capable of detecting information relating to a toner content in said developing device; an exchange detecting portion configured to detect information for discriminating an event of exchanging operation of said supply container; and a controller configured to control a supplying operation from said supply container, on the basis of a detection result of said content sensor, wherein said controller is capable of prohibiting an image forming operation on the basis of the detection result of said content sensor and is capable of releasing the prohibition of the image forming operation on the basis of the detection result of said exchange sensor, and wherein after releasing the prohibition of the image forming operation on the basis of the detection result of said exchange sensor, characterized in that said controller is further configured to acquire a cumulated information relating to a toner consumption amount for each image formation, said controller is configured to continue permission of the image forming operation irrespective of the detection result of said content sensor when the information relating to the toner consumption amount cumulated every image formation indicates an amount less than a predetermined amount, and when the information relating to the toner consumption amount after the release of the prohibition of the image forming operation reaches the predetermined amount, said controller is configured to determine whether to prohibit the image forming operation on the basis of the detection result of said content sensor after the information relating to the toner consumption amount reaches the predetermined amount. an image bearing member capable of carrying an electrostatic image; a developing device configured to develop an electrostatic image formed on said image bearing member into a toner image, using a developer including toner and carrier; an exchangeable supply container configured to supply the developer into said developing device; a content sensor capable of detecting information relating to a toner content in said developing device; an exchange detecting portion configured to detect information for discriminating an event of exchanging operation of said supply container; and a controller configured to control a supplying operation from said supply container, on the basis of a detection result of said content sensor, wherein said controller is capable of prohibiting an image forming operation on the basis of the detection result of said content sensor and is capable of releasing the prohibition of the image forming operation on the basis of the detection result of said exchange sensor, and wherein after releasing the prohibition of the image forming operation on the basis of the detection result of said exchange sensor, characterized in that said controller is further configured to acquire a cumulated information relating to a toner consumption amount for each image formation, said controller is configured to continue permission of the image forming operation irrespective of the detection result of said content sensor when the information relating to the toner consumption amount cumulated every image formation indicates an amount less than a predetermined amount, and when the information relating to the toner consumption amount after the release of the prohibition of the image forming operation reaches the predetermined amount, said controller is configured to determine whether to prohibit the image forming operation on the basis of the detection result of said content sensor after the information relating to the toner consumption amount reaches the predetermined amount.