A vehicle passenger detecting device includes a judging circuit (6), which judges whether a passenger seated on a seat (1) is a child or not based on a load acting on each of areas of a seat portion (1a) of the seat for a vehicle, and the judging circuit (6), with a fastened sate of a seat belt (5a), judges whether or not a total load acting on the entire area of the seat portion is within a predetermined range, and when the total load is within the predetermined range, if a front outer load acting on a front outer area is a first threshold or more and the ratio of the front outer load to a front inner load acting on a front inner area is a second threshold or more, or the ratio of both outer loads acting on both of outer areas to both inner loads acting on both of inner areas is a third threshold or more, the judging circuit judges (6) that a seated passenger is a child.