The present invention is intended to achieve an improvement in the horizontal resolution of an active matrix semiconductor display device. In accordance with the present invention, by supplying a modulated clock signal obtained by frequency modulating a reference clock signal at a constant period to a driving circuit of an active matrix semiconductor display device or to a driving circuit of a passive matrix semiconductor display device, signal information (the presence or absence of an edge, the extent of nearness) relative to the vicinity of the sampling of video signals (image signals) sampled on the basis of this modulated clock signal can be written to the corresponding pixels of the semiconductor display device as shading information. The driving method of the present invention makes use of a phenomenon which apparently makes the resolution of an image display higher owing to the shading information (visual Mach phenomenon and Craik-O'Brien phenomenon).