Abstract: The present method involves heating a blank, a shank and a welding material in an instantaneous heating process wherein a temperature instantaneously rises at a rate of 500-1000° C./min.; and cooling the blank and the shank at a temperature of 700-1200° C. for a short period of time thus integrating the blank and shank into a cutting tool. The instantaneous heating process is preferably a light heating process by a halogen lamp. A welding chamber for the blank controls both pressure and atmosphere, and is provided with a desired degree of vacuum. In this manner, a thermal deterioration of a diamond blank, a welding metal or a shank material is prevented.