PURPOSE: To shorten a quiescent time, to reduce power consumption, and to efficiently operate a copying machine when copying a continuous number of sheets, by controlling a start time of a copying operation after the copying machine has stopped.

CONSTITUTION: When copying continuously, a drop of a temperature T of a fixing roller 2 is monitored by a CPU7, and at a lower limit temperature Td, a command is sent to a machine controller 8, and the copying operation is stopped temporarily. By heating efficiency of a heater 1, storage efficiency of the fixing roller 2, size of transfer paper, a passing speed, an interval, etc., the temperature T of the fixing roller 2 and the number sheets P of fixable paper 4 are decided unequivocally. The CPU stores them, immediately derives a temperature of the fixing roller for fixing the remaining number of copying sheets from its portion by said data at the quiescent time, and starts copying immediately when a temperature of the fixing roller 2 has reached this temperature.