The invention provides a spatial light measuring system, which comprises an illuminance measuring instrument for measuring an illuminance on the ground in a state where an illumination facility is new in a running direction of a traveling vehicle at predetermined intervals, the illuminance measuring instrument and an image pickup device which are mounted on the traveling vehicle for continuously acquiring images including an illumination facility at the predetermined time intervals, a speedmeter for detecting a speed of the traveling vehicle and an arithmetic device, wherein the arithmetic device is configured to store illuminance data acquired by the measurement in a new state as initial data, to make the traveling vehicle to run after acquiring the initial data, to save illuminance data acquired. by the illuminance measuring instrument as daily management data, and to specify an illuminance measuring position and an image acquiring position based on the speed of the traveling vehicle as detected by the speedmeter and the arithmetic device has a correction coefficient due to a distance from the ground to an illuminance measuring instrument mounting position and a correction coefficient due to the speed of the traveling vehicle and is configured to correct daily management data into illuminance data on the ground based on both the correction coefficients and to judge the soundness of the illumination facility based on a comparison between the illuminance data as corrected, the initial data and based on the images as acquired.