To reduce a quantity of a flash generated at the time of a chamfering processing.

The compound saw blade of the cutter is provided with: a discoid cutter blade in which a number of blades are formed on the outer periphery and a carbide tip is mounted at the top of each of blade to cut a gypsum board out a given length by a rotating action; and a discoid chamfering blade 33 in which a carbide tip 37 is formed at a cutting edge of each cutting tooth 33a with the diameter set smaller than that of the cutting blade which are formed on the outer periphery, a carbide tip 37 is formed at cutting edge of each cutting tooth 33a for performing a chamfering process to the gypsum board with the carbide tip 37 succeeding to the cutting action with the cutting blade rotating as unified with the cutting blade. The carbide tip 37 of the chamfering blade 33 is designed to be a face angle more than -30or less than -16.7including both ends and a side rake angle more than -15or less than -2.4including both ends.