Image display system 10 comprises: a plurality of display devices 111; an image processing unit for receiving input of a plurality of input video signals and generating an output video signal for each display device in accordance with a layout for the display devices from the input video signals; a pattern signal generation unit for generating pattern signals indicating a plurality of different test pattern images; a selector for receiving input of the output video signals and the pattern signals and selecting and outputting either the output video signals or the pattern signals; imaging device 120 for capturing an image of the test pattern images displayed on the respective display devices; and a control device 140 for analyzing the captured image captured by the imaging device and generating control information for controlling the image processing unit, based on analysis results.