PURPOSE: To carry out the honing work and the plane grinding work of a throwaway tip in a single process.

CONSTITUTION: A grinding wheel 10 for honing having an elastic abrasive grain layer, and a grinding wheel 11 for plane grinding having a hard abrasive grain layer are provided oppositely, and after a carrier 12 having a carrier hole 13 is arranged between the grinding wheels 10 and 11, a tip C for grinding is inserted into each carrier hole 13 opposing the cutting edge side C2 of the tip to the grinding wheel 10 for honing, and the seating surface C1 of the tip to the grinding wheel 11 for plane grinding. After the grinding surfaces of both grinding wheels are brought into contact with both surfaces of the tip C, both grinding wheels are rotated, and the carrier 12 is planetary-rotated between both the grinding wheels, so as to plane grind the seating surface C1 of the tip while honing the cutting edge E of the tip.