A passenger detection system for detecting a sitting of a passenger on a seat of a vehicle has a capacitive passenger detection electrode which is embedded in the seat to detect the sitting, a surface unit attached to an upper surface of the seat, a driving unit which applies a voltage between the passenger detection electrode and a vehicle GND, and a detection unit for detecting a capacitance between the passenger detection electrode and the vehicle GND. At least a covering portion of the surface unit is rendered electrically conductive. The passenger detection electrode is covered with the covering portion. Thus, a sitting of the seat can be substantially detected by the passenger detection system.