1. A driving method of a plasma display device comprising: constituting one field period by a plurality of subfields having a predetermined luminance weight; selecting a plurality of combinations from arbitrary combinations of the subfields and creating a combination set for display; and controlling light emission in a discharge cell and displaying a gradation, using the combination set for display, wherein a plurality of combination sets for display having a different number of combinations is provided, wherein, in one direction, a spatial differentiation of an image signal in said plasma display device is calculated based on a first image signal difference between two pixel points on the plasma display device, and wherein the image signal for which the spatial differentiation is calculated being red, green and blue, and wherein a first number of combinations of subfields in the combination set for a first spatial differentiation of said image signal is smaller than a second number of combination of subfields in the combination set for a second spatial differentiation of said image signal, wherein, the first spatial differentiation is larger than the second spatial differentiation.