At least one exemplary embodiment is directed to an apparatus which includes an original stage, to hold an original, which moves in a scan direction, an illumination optical system configured to illuminate the original held by the original stage with exposure light, a substrate stage configured to hold a substrate and to move in a scan direction, a projection optical system configured to project a pattern of the original onto the substrate with the exposure light, and an irradiation unit configured to irradiate the original held by the original stage. Irradiation by the irradiation unit and movement of the original stage in the scan direction are carried out substantially in parallel with each other so as to remove a contaminant on the original.