Disclosed is a dual-cutting method devoid of useless strokes of cutting blades across a workpiece. The work piece has cross lines drawn in the form of lattice, and it is divided into the intermediate and opposite side zones. Two lines of substantially equal length are selected in the intermediate zone to be cut simultaneously every time the two cutting blades have been moved line-to-line distance for indexing. One of the two cutting blades is allotted to one of the opposite side zones, and the other cutting blade is allotted to the other side zone. As is the case with the cutting in the intermediate zone, two lines of substantially equal length are selected in the opposite side zones to be cut simultaneously every time the two cutting blades have been moved line-to-line distance for indexing.