An occupant detecting device comprises plural cells provided at a seating part of a vehicle seat and defined by an array of rows in a width direction of the vehicle seat and columns in a cross direction of the vehicle seat for detecting partial pressures of the seating part, a total pressure value calculating means for obtaining a total pressure value by summing up the detected partial pressures, a determining means for determining a condition of the vehicle seat on which an adult passenger is sitting based on a comparison result between the obtained total pressure value and a determining value threshold, a temperature sensor for detecting temperature, and a correcting means for correcting at least one of either the total pressure value calculated based on the detected temperature or the determining value threshold.