The invention relates to a machining method of a cutter. The method comprises the following steps that 1, two mutually-perpendicular cutting surfaces are cut at the end part of a hard alloy base body,a welding platform is formed by the cutting surface parallel to the bottom of the hard alloy base body and the hard alloy base body, the other cutting surface is a welding surface, a chip groove is formed in the welding platform, a positioning surface is reserved on the side, close to the welding surface, of the chip groove, and finally a clearance surface in a shape of a concave arc surface is formed in the side, away from the welding surface, of a protruded part of the end of the hard alloy base body; 2, diamond is welded to the end of the hard alloy base body to form a diamond cutter; and3, a laser cutting method is adopted for machining the cutter so that the cutter can be provided with a first rear cutter surface, a second rear cutter surface and a cutter edge. The technology methodis simple, the machining precision is high, the surface of the diamond is coated with a coating, transmission and reflection of laser can be effectively prevented, and the machining efficiency and quality of the cutter are improved.