To solve a problem that cutting bending, vibration and noise are generated in a saw blade, and the life of the saw blade is lowered because an insert plate as a saw blade side face support of a band saw machine or a circular saw machine is arranged spaced apart from a cutting site even after passing through a cutting maximum width to avoid interference with a material to be cut such as a roundwood and a hexagonal wood up to now.

Two insert plates located in a right and left positions of the material to be cut is made movable along a contour side face of the material to be cut and a saw blade is supported moving the same so as to approach after passing a cutting maximum width. Therefor, one side faces of the insert plates is formed into a tapered shape so as to dive into the lower side of the material to be cut.