In an occupant weight detection system, a pair of weight detection units are mounted along upper faces of base members fixed to a floor of an automobile. A square-frame-shaped linking member made of an iron sheet is interposed between the pair of weight detection units and a pair of seat rails. The pair of weight detection units are integrally linked by the linking member to maintain a positional relationship to each other at a predetermined relationship. Therefore, it is possible to prevent these weight detection means from being mounted in a state in which they are twisted or displaced relative to each other, thereby maintaining the detection accuracy.