An occupant detection apparatus includes a first detection unit, a second detection unit, and an occupant presence determination unit. The first detection unit detects an occupant present in a first region or a second region, among the plurality of regions. The second detection unit detects an occupant present in the second region or a third region, among the plurality of regions. The occupant presence determination unit determines whether an occupant is present in each of the first region, the second region and the third region, based on a first detection result obtained by the first detection unit and a second detection result obtained by the second detection unit.