1. An image display device for displaying an image on the basis of image data comprising: an image feature quantity calculating portion which calculates a plurality of image feature quantities based on a luminance histogram of the image data; an expansion coefficient determining portion which determines an expansion coefficient based on the plurality of image feature quantities by referring to a predetermined expansion coefficient lookup table; a luminance range expansion processing portion which performs a luminance range expansion process on the image data using the expansion coefficient, the luminance range expansion process being a process to extend a range of luminances of the image data; and an expansion substituting portion which, in case where a current frame ideal expansion coefficient equals a second previous frame ideal expansion coefficient, but does not equal a first previous frame ideal expansion coefficient, substitutes the current frame ideal expansion coefficient with a first previous frame expansion coefficient to generate a current frame expansion coefficient, the current frame ideal expansion coefficient being an expansion coefficient determined by the expansion coefficient determining portion based on the plurality of image feature quantities of a current frame referring to the predetermined expansion coefficient lookup table, the first previous frame ideal expansion coefficient being an expansion coefficient determined by the expansion coefficient determining portion based on the plurality of image feature quantities of a frame previous by one the current frame referring to the predetermined expansion coefficient lookup table, the second previous frame ideal expansion coefficient being an expansion coefficient determined by the expansion coefficient determining portion based on the plurality of image feature quantities of a frameprevious by two the current frame referring to the predetermined expansion coefficient lookup table, the first previous frame expansion coefficient being an expansion coefficient used in the luminance range expansion process of the frame previous by one the current frame, wherein the image data is moving picture data, the expansion coefficient determining portion determines the expansion coefficient for each frame of the moving picture data by referring to the predetermined expansion coefficient lookup table, and the luminance range expansion processing portion performs the luminance range expansion process on the image data using the current frame expansion coefficient as the expansion coefficient.