An ozone filtering mechanism in an image forming apparatus such as office copiers, etc. and its arrangement, wherein various component elements disposed in the image forming apparatus in such a manner that a flow path for a discharge current of ozone gas generated from a corona discharger and a flow path for heat current from a heat source such as a light source, etc. may be centralized at one place, thereby enabling a single ozone filter to be disposed at this portion of the centralized flow paths for perfect ozone filtration. Presence of the heat current at the time of the ozone filtration promotes adsorption and decomposition of ozone to augment the filtering effect to the maximum possible extent.