A robot system includes a position information emitting unit including a light emitter to emit a light including phase information and a supersonic wave emitter to emit a supersonic wave, and a robot including a light receiver to receive the light, a supersonic wave receiver to receive the supersonic wave, and a position determining part to determine a relative position of the robot with respect to the position information emitting unit based on the phase information of the light received through the light receiver and the supersonic wave received through the supersonic wave receiver. Thus the robot system can precisely determine the position of the robot regardless of external environments, and reduce cost of a configuration of the system.