A chemical filter, which removes chemical pollutants from gas and controls temperature fluctuation of the gas before and after passing through the filter to within a predetermined range, is arranged in a portion of a ventilation path extending from a machine chamber housing at least a portion of an air conditioning unit to a main body chamber housing an exposure apparatus main body. Accordingly, the atmosphere around the exposure apparatus main body arranged downstream of the chemical filter is kept chemically clean, and the temperature fluctuation of the gas, of which the temperature is set to a target temperature by the air conditioner, after passing through the chemical filter is limited. That is, occurrence of a problem such as an illumination reduction caused by tarnish of optical members and an increase of the temperature fluctuation amount of the gas supplied into the main body chamber can be effectively limited.