A flight control system for a flying object comprises a flying object, a navigating means provided in the flying object, a position measuring unit 17, a flight control unit 18 for controlling the navigating means, and a main arithmetic control unit 19 for controlling the position measuring unit and the flight control unit, and in the flight control system for a flying object, the position measuring unit has a GPS device 23 for measuring a ground coordinate of the flying object and a vertical camera 13 for taking a digital image below the flying object and measures an altitude of the flying object based on images at two points taken by the vertical camera, on ground coordinates of the two points measured by the GPS device, and on a focal length of the vertical camera, and the main arithmetic control unit controls the navigating means via the flight control unit based on the measured altitude and makes the flying object fly at a predetermined altitude.