A control system 9 according to the present invention is mounted on a moving object. The control system 9 includes: an observing device 92 which transmits observation result data indicating an observation result of surroundings of the moving object; a first control instruction device 91 which transmits first control data indicating the control contents determined based on the observation result data; a movement control device 93 which controls movement of the moving object; and a relay device 95 which relays the first control data transmitted from the first control instruction device 91, to the movement control device 93. When a second control instruction device 94 which transmits second control data indicating the control contents determined based on the observation result data is provided to the control system 9, the relay device 95 transmits the second control data instead of the first control data, to the movement control device 93.