The invention provides an illuminance measuring system, which comprises an illuminance measuring instrument which comprises a first communication unit and is moved by a moving vehicle, a position measuring means which comprises a second communication unit and measures a three-dimensional position of the illuminance measuring instrument and a data collector which comprises a third communication unit and a storage unit for storing positional information data of a predetermined measuring point, wherein the data collector moves the moving vehicle to the measuring point based on a position of the illuminance measuring instrument and the positional information data, an illuminance is measured and a position of the illuminance measuring instrument is measured, and wherein the data collector obtains an illuminance measurement result from the illuminance measuring instrument, obtains a measuring position from the position measuring means, and collects the illuminance measurement result and the measuring position in association with each other.