To realize a very smooth and long time spot-facing work by a method wherein a simultaneous cutting work with chain saw blades is executed on the surfaces of two building materials from the edge faces of the two building materials arranged so as to lay one on the top of another.

Tips 5 form the blade part of a chain saw blade by being fixed to cutting links, which consists of a plurality of rows of endless chains arranged to the running direction of the chain, at required intervals to the running direction of the chain and to the direction normal to the running direction of the chain. By advancing a chain saw 9, in which this chain saw blades are employed and which is rotated to the direction indicated with the small arrow, from the edge face side of building materials K1 and K2 arranged so as to lay one on the top of another to the direction indicated with the large arrow, spot-faced surfaces Z1 and Z2 are cut at once on the top and bottom surfaces of the building materials K1 and K2. In addition, since the cutting edge of a cutting blade is provided so as to lean to a right side of a left side to the running direction of the chain or the cutting surface of a workpiece, the cutting resistance of the chain is reduced and the good flow of saw dust is realized, resulting in enabling a long time cutting.