1. A vehicle occupant detection apparatus, comprising: an image pickup device for imaging an area that includes a position of a vehicle occupant within a vehicle compartment; vehicle occupant determination means for making a determination about the vehicle occupant; a light emitting element for emitting auxiliary light into the vehicle compartment that includes an imaging area of said image pickup device; storage means for storing imaging information provided by said image pickup device; comparison means for comparing imaging information provided through further imaging operation by said image pickup device and the imaging information stored in said storage means, to provide a difference between the imaging information provided through the further imaging operation and the stored imaging information; and imaging abnormality determination means for determining abnormality of the imaging information based on the difference provided by said comparison means.