To provide an image display device capable of superimposing an endoscope image and a diagnostic image.

This image display device comprises: an endoscope 2 for successively picking up the endoscope images while moving an evaluation panel 5 provided on the front surface of the endoscope and composed of: a two-dimensional grating in parallel in the vertical direction of the visual field of the endoscope; and an endoscope device body 6 for calculating a magnification rate from the center position of the endoscope image by using each endoscope image of the two-dimension grating successively image-picked up by the endoscope 2, obtaining the phase distribution by using each endoscope image of the two-dimensional grating successively image-picked up by the before-mentioned image pickup means (endoscope 2), calculating a two-dimensional correction vector for correcting a two-dimensional image distortion due to the lens aberration of the endoscope image from the obtained phase distribution, calculating three-dimensional correction vector by compositing the respective calculated two-dimensional correction vectors with the one of the close endoscope image picked up by the image pickup step, deforming the diagnostic image photographed by an image diagnostic device so as to be superimposed with the endoscope image by using the calculated three-dimensional correction vector and the calculated magnification rate and superimposing and displaying the deformed diagnostic image and the endoscope images successively picked up by the endoscope 2.