A multi-projection display system is provided with a plurality of sensor units corresponding to projector units. The sensor units detect brightness for each color in a projected image that is projected on a screen and supply the detection results. The projector unit generates a brightness correction table on the basis of the image signal of a specific picture element of the projected image realized by an adjacent projector unit and on the basis of the brightness of the specific picture element of the projected image of the adjacent projector unit that is detected by a sensor unit for matching the brightness of the image projected by its own projector unit with that of the adjacent projector unit, refers to the brightness correction table to correct brightness for each color of the image signals that are received as input, and projects onto a screen the light of each color in accordance with the corrected image signals.