Idling start-stop system and idling start-stop control method

The invention provides an idling start-stop system. The idling start-stop system can simply achieve an idling start-stop function by combining a conventional engine ECU and a starter generator ECU designed for a starter generator without making a significant design change to a conventional engine ECU and by controlling the engine ECU and the starter generator ECU. The idling start-stop system comprises the engine and the engine ECU; a starter generator and a starter generator ECU which work as a starter motor when the engine is started and work as a generator after the engine is started. and acrankshaft sensor which is arranged on the starter generator and detects the rotational speed of the starter generator. The engine ECU and the starter generator ECU are arranged in a split manner, the starter generator ECU is used for controlling the power supply of the crankshaft sensor, and the detection result relating to the rotational speed of the starter generator detected by the crankshaftsensor is transmitted to