An apparatus for detecting the passenger occupancy of a vehicle includes, at least two image pickup sections provided at a specified distance, a measuring section measuring a distance to an object on the basis of the at least two images acquired by the at least two image pickup sections, a reference data providing section providing reference data relating to the distance from the image pickup sections to a seat in accordance with the position of the seat, and a detection section detecting the passenger occupancy of the seat on the basis of the distance measured by the measuring section and the reference data.