To provide an illumination system that improves measurement precision of luminance of an irradiated surface by effectively correcting shading.

The illumination system comprises: a luminaire 1 having an illumination load 10 and a lighting control portion 11; and an image sensor 2 having an imaging portion 20 and a control portion 21. The illumination control portion 11 controls light output of an illumination load 10 so that the luminance of the entire irradiated surface A computed by the control portion 21 reaches predetermined luminance, and the control portion 21 has a shading correcting function of performing processing for controlling the lighting control portion 11 so as to irradiate the irradiated surface A with light uniformly; processing for imaging the irradiated surface A by the imaging portion 20; and processing for computing, by pixels, correction rates each obtained by dividing luminance of each of pixels constituting image data 3 acquired through the imaging by the imaging portion 20 by a reference value based upon luminance of a center part 30 of the image data 3. The illumination control portion 11 thereby computes luminance of the entire irradiated surface A by using luminance of each pixel of the image data acquired through the imaging by the imaging portion 20 by the correction rate in such a case.