An exposure apparatus comprises an optical system configured to illuminate a reticle, including an imaging optical system having an optical element, a reflecting surface which reflects light toward the optical element, and a processor which extracts information from a first signal based on first light which is incident on the imaging optical system and reflected by the reflecting surface and a surface of the optical element, and information from a second signal based on second light which is incident on the imaging optical system, and which obtains information indicating a surface condition of the optical element using the information extracted from the first and second signals.