1. A method of inspecting an area defect on an image display panel capable of displaying a two-dimensional digital image which comprises a plurality of pixels disposed in orthogonal X and Y axes in the digital image, said method comprising the steps of: obtaining original two-dimensional image data representing respective pixel values of respective pixels of an original two-dimensional digital image from a display panel to be inspected when said panel is so operated as to display said original two-dimensional digital image at a uniform gradation state; applying two-dimensional Wavelet transform to the original two-dimensional digital image data to thereby obtain a two-dimensional Wavelet transformed digital image which has an X-axis and Y-axis low pass information image portion, an X-axis high pass information and Y-axis low pass information image portion, an X-axis low pass information and Y-axis high pass information image portion, and an X-axis and Y-axis high pass information image portion, each of which is reduced to one-quarter in area as compared with that of the two-dimensional original digital image and includes a plurality of blocked pixels each measuring 2.times.2 pixels of the original digital image; and determining whether or not the display panel under inspection is defective based on the pixel values of the blocked pixels of the X-axis and Y-axis high pass information image portion of the Wavelet transformed digital image.