PURPOSE: To uniformize the quality of sintered ore always with the optimum air quantity and contrive to economize the electric power consumption of a main blower by executing the control to determine the air quantity leakages of respective window boxes and adding the total sum thereof to set air quantity.

CONSTITUTION: Displacement meters 11 are built into wear bars 8 in the upper parts of the respective window boxes 2 of a sintering machine 17. An electric signal in the spacing between a sill bar 7 and the wear bar 8 is outputted to a process computer 9 when a pallet carriage 1 passes on the displacement meter 11. The computer 9 calculates the air quantity leakages for each of the window boxes 2 and outputs the signals thereof to respective window box damper servocontrol motors 10 to open and close respective dampers 3, thereby controlling the air quantities. The computer 9 calculates the sum total of the above- mentioned air quantity leakages at the same instant and outputs the electric signal corresponding thereto to the main blower motor 14 or main damper servocontrol motor 13. The control to add the air quantity leakage to the set air quantity by controlling the rotating speed of the main blower and the main blower damper 4 is thereby executed.