DEVELOPER REPLENISHING DEVICE AND IMAGE FORMING DEVICE USING IT

PROBLEM TO BE SOLVED: To provide an image forming device capable of surely detecting the amount of developer remaining in a developer container without installing a complicated sensor mechanism. SOLUTION: The developer replenishing device 2 is provided with the container 10, a driving motor 15 for rotating the container 10, a carrying screw 6 for supplying the developer to a developing device 54, a remaining amount detecting sensor 5 for detecting the amount of the developer remaining in the developer storing part 4, and a concentration sensor 33 is arranged in the developing device. The amount of the developer discharged from the container per one rotation is calculated by a control part 62 based on the relation between the rotational amount of the carrying screw and the rotational amount of the container, then, the remaining developer amount in the container is calculated based on the discharged developer amount. Then, the remaining developer amount in the container is obtained without installing the sensor, etc., in the container.