PURPOSE: To know the secure maintenance time of a long-life body to be detected by transmitting the rotation of an image carrier in an speed reduction state and detecting the rotation, and display-playing the state that the number of revolution attains a value corresponding to the maintenance time of the body to be detected.

CONSTITUTION: The rotation of a photosensitive drum 1 are transmitted to the input shaft 13 of a switch operating mechanism 10 and the output shaft 15 makes a nearly one rotation when the drum 1 rotates specified times. Then, the eccentric projecting part 9a of an eccentric cam 9 fitted to the output shaft 15 through a unidirectional rotation clutch 16 presses the operating lever 11a of a detection switch 11, which is operated. Consequently, a display part 12 turns on to indicate that the cleaning time of the developer recovery box 7 of, for example, a cleaning device 2 comes, and following copying operation is stopped. Then, an operator draws out and cleans the developer recovery box 7. Thus, the maintenace time of the long-life body to be detected is known securely.