PURPOSE: To extremely exactly perform precision finishing for the surface of a working piece so that wear of an abrasive grain may continuously increase in the direction from a front end to a rear end.

CONSTITUTION: A broaching tool has base substance 26 provided with a coating 28. This base substance 26 is constituted of a carrying layer 40 into which a diamond grain is embedded. An outside face 24 of this base substance 26 is projected in the pulling direction 20 and in the direction from the front end 34 to the rear end 36. The diamond grain 42 which is supported by this base substance 26 and has a uniform size is worn in parallel to a surface existing in the pulling direction 20. As a result, wear of diamond grain which continuously increases in the direction from the front end 34 to the rear end 36 is generated. Therefore, a working piece can be precisely finished.