An exposure apparatus that exposes an object to be exposed with light from an EUV light source. The light has an exposure wavelength component and a non-exposure wavelength component. The exposure apparatus has a detector that independently detects the quantity of light of the exposure wavelength component and the quantity of light of the non-exposure wavelength component of the light. Therefore, for example, even if the quantity of light of the exposure wavelength component and the quantity of light of the non-exposure wavelength component individually fluctuate, it is possible to accurately ascertain fluctuations in the characteristics of the optical system resulting from irradiation heat. As a result, it is also possible to achieve a high performance mirror adjustment system.