In one embodiment, a substrate inspection apparatus performs, in its maintenance mode, operations including: guiding a light emitted from an illuminating unit to an imaging device via a light-guiding member disposed in a casing; judging whether or not a level of a brightness signal obtained by the imaging device falls within a predetermined allowable range when a light emitted from the illuminating unit falls on the imaging device via the light-guiding member; and alarming, if it is judged that the value of the brightness signal is out of the predetermined allowable range, that replacement of the illuminating unit is required.