It is an object of the present invention to provide an energy-saving image forming apparatus capable of fixing toner in a reliable manner to enhance the quality of images, control the temperature of toner residue to reuse the toner in a reliable manner, and reduce the power consumption of the apparatus. In a copier, a photoconductive drum carries a toner image to be transferred to a recording medium, a heater of a fixing unit fixes the transferred toner image on the recording medium, and a cleaning unit removes toner residue on the photoconductive drum after transfer. The whole copier is covered with a housing, a first ventilation system ventilates the inside and outside of the housing, and a controlling section regulates the amount of ventilation by the first ventilation system in accordance with an output from a temperature sensor for detecting the temperature of the cleaning unit. As a result, it is possible to effectively reuse the collected toner and ensure excellent quality images.