The data conversion device of the present invention includes: a coding section for replacing (i) one or more components constituting the display data of each pixel and other one or more components constituting display data of a pixel existing around that pixel on a screen with (ii) one or more average values of both the components so as to reduce an amount of data; and a decoding section for reading out compressed data from a frame memory and then allotting the average value as display data for each corresponding pixel. Therefore, unlike a case of adopting a conventional general data compression method, the data conversion device of the present invention can prevent deviation between original display data and display data obtained by a compression/restoration process from becoming large. Further, the data conversion device of the present invention can suppress the capacity of a necessary frame memory by compression (reduction) of data, and at the same time suppress a decrease in display quality due to the compression (reduction) of data.