In a plasma display, image data are mapped on N subfields, and the subfield with the greatest weight is determined from among the mapped subfields. When the subfield with the greatest weight is the Kth subfield (K>M), grayscales of the image data are expressed with the mapped data of the (K−M+1)th subfield to the Kth subfield, and the mapped data from the first subfield to the (K−M)th subfield may be ignored.