An exposure apparatus includes an illumination optical system which illuminates a pattern formed on a mask with light from a light source, a movable mask stage for holding the mask, a projection optical system which guides light from a pattern of the mask to a wafer, a movable wafer stage for holding the wafer, a shielding member which forms an optical path space including an optical path of exposure light and a space surrounding the optical path space at, of a space through which the exposure light passes, at least one portion between the illumination optical system and the mask stage, between the mask stage and the projection optical system, or between the protection optical system and the wafer stage, a first gas supply device for supplying an inert gas to the optical path space, a chamber surrounding the wafer stage, the projection optical system and the shielding member, and a reduction device for reducing a change in total light quantity of the exposure light reaching the wafer that is caused by movement of at least one of the mask stage and the wafer stage.