An image projection system includes projection means for projecting an image on a transmission type screen from a rear surface side of the screen, standard image information generating means for generating standard image information of a standard image, image capturing means for capturing an image on the rear surface of the screen from an inside of a casing in which the projection means is housed, the image capturing means capturing the standard image projected onto the screen from the projection means, which receives the standard image information from the standard image information generating means, removing means for removing influences of external light from the standard image projected from the projection means onto the screen, correction value computing means for computing a correction value on the basis of image information of the standard image from which the influences of the external light are removed by the removing means, correction value storage means for storing the correction value information obtained by the correction value computing means, and correction means for correcting image information from a picture signal source by using the correction value information stored in the correction value storage means, and supplying the corrected image information to the projection means.