The present invention presents an exposure device, which includes an object stage on which the object is to be set, at least one aperture member for splitting a light beam from an optical source into first and second light beams, first and second spatial light modulators for spatially modulating the first and second light beams, respectively, first and second projection optical systems for irradiating the object with the first and second light beams, at least one first optical sensor for detecting intensity of the light beam from the optical source, one or more second optical sensors for detecting intensities of the first and second light beams from the first and second projection optical systems, respectively, and a decision section for diagnosing status of a route between the aperture member and the object, based on the results of the first and second sensors.