PURPOSE: To permit efficient exchange of cartridges by outputting exchange instruction signals for respective storage parts in accordance with the logical conditions of the output of means for counting the number of prints and the output of a 1st detecting means for detecting the amt. of the toner in the toner storage part of 2nd detecting means for detecting the amt. of the recovered toner in the toner storage part.

CONSTITUTION: This device is provided with the means 23, 25 for counting the number of prints, the 1st detecting means 22 for detecting the amt. of the toner in the toner storage part 12, and the 2nd detecting means 24 for detecting the amt. of the recovered toner in the recovered toner storage part 17. The exchange instruction signals for the respective storage parts 12, 17 are outputted in accordance with the logical conditions of the outputs of the counting means 22, 25 and the output of the 1st or 2nd detecting means 22 or 24. For example, the exchange instruction is executed by the AND of the outputs for the 1st cartridge having the toner storage part 12 and the exchange instruction is executed by the OR of the outputs for the 2nd cartridge having the recovered toner storage part 17. The efficient exchange of the respective cartridges having the toner storage part 12 and the recovered toner storage part 17 is thereby permitted.