The present invention provides an exposure apparatus that exposes a substrate via a projection optical system, the apparatus including a supply unit including a first channel to which a first gas containing air is supplied, a second channel to which a second gas higher in oxygen concentration than the first gas is supplied, and a third channel to which a third gas lower in oxygen concentration than the first gas is supplied, and configured to generate a mixture gas by using at least two of the first gas, the second gas, and the third gas, and supply the mixture gas to a space between the substrate and the projection optical system.