The present invention provides an exposure apparatus which exposes a substrate, the apparatus including an adjustment unit configured to adjust an oxygen concentration in a space between the projection optical system and the substrate, a measuring unit configured to measure an illuminance of light applied to the substrate, and a control unit configured to control the measuring unit so as to measure illuminances of light applied to the substrate a plurality of times during irradiation of the substrate with light from the projection optical system, configured to calculate, based on each of the illuminances measured the plurality of times, an oxygen concentration value corresponding to the measured illuminance on each time and configured to control the adjustment unit so as to set the oxygen concentration in the space to the calculated oxygen concentration value.