PURPOSE: To prevent accumulation of delay, to hold staying time of individual materials in a furnace, to make heat treating effect uniform and to prevent an irregularity in quality by recovering delay to time shorter than 1/2 of a material conveying period.

CONSTITUTION: A material 12 is so charged from an inlet 2 of a roller hearth furnace that intervals (g) of materials 12 become equal on rollers 8 in the furnace. When the passage of the rear end of the material 12 is sensed by a sensor 16 and it is advanced at a distance corresponding to the gap (g), the rollers 8 are stopped, an openable door 4 is opened, and the material 12 is charged by the rotations of a charging roller 6 and a charging roller 7 in the furnace. The arrival of the end of the material 12 is sensed by the sensor 16, the roller 8 is restarted, and the door 4 is closed. Even when the end of the material 12 is sensed by a sensor 17, the material 12 is similarly extracted, and the door 5 is closed. A method of regulating the conveying speed of the roller 8 has steps of counting stopping time for stopping to charge and extract by the roller 8, and recovering delay due to the stop to time shorter than 1/2 of a material conveying period after the stop.