According to an embodiment of the present invention, an image forming apparatus having an automatic document carrier device including a plurality of sensors arranged in a path where source documents to be read are carried; a plurality of motors configured to detect the positions of the source documents by these sensors and to carry the source documents at a predetermined speed; a cooling fan to be rotated to reduce the ambient temperature; a fan motor configured to drive the cooling fan; and a carrier control unit configured to control the plurality of sensors, the plurality of motors and the fan motor, wherein the carrier control unit detects passage of the source documents by any of the plurality of sensors, estimates a time when the source documents are discharged into the discharge tray, and stops the fan motor around the estimated time.