Abstract: A robot control system includes a robot that screw-fastens a sub-component placed in a main-component to the main-component, a robot control unit that controls the robot, and a display as an output unit through which the robot control unit outputs a message to an operator. The robot control unit determines whether or not the robot can screw-fasten the sub-component to the main-component by itself. Then, when the robot control unit determines that the robot cannot screw-fasten the sub-component to the main-component by itself, the robot control unit outputs a cooperation message to an operator through the display.