A control system for collectively supervising a plurality of copiers or similar image forming apparatuses connected to a control device by communication lines with or without the intermediary of communication control units. To down-load data relating to image formation, the control device determines whether or not a copier of interest is in an inoperative state and, if it is in an inoperative state, automatically sends the data to the copier via a telephone line, an exchange, and a communication control unit. This data is written to storing means built in the copier. To up-load data relating to image formation, the control device causes each copier to automatically send the data stored in the storing means and stores the data in memory means. Up-loading is effected at an optimal time other than the time when the copier is performing an automatic adjustment, is in use, or is quite likely to be used.