An image display device for displaying an image on the basis of an image signal supplied from an image supply device includes a brightness detecting section that detects a gray level which characterizes brightness of a predetermined pattern image from a pattern image signal when the predetermined pattern image is supplied from the image supply device; a storing section that stores a reference gray level predetermined in the pattern image; a correction parameter setting section that sets a correction parameter for compensating by a difference between the gray level detected by the brightness detecting section and the reference gray level stored in the storing section; and a correcting section that corrects the brightness of the image signal supplied from the image supply device on the basis of the correction parameter.