To precisely polish various knife blades having different cutting blades, on the surface of a grinding wheel by downward projecting the lower end of a height adjusting member retractably screwed onto a pedestal body.

In such a case that a cutting blade Sa of a knife S is polished at a polishing angle which is larger than a front end angle (a) of a pedestal body 1, the front end of a height adjusting bolt 4 is projected from a top surface 11 while the lower surface of the knife S is supported a linear front end contour line 11A and a dot-like height adjusting bolt 40, and the upper surface of the knife S is pressed by a fastening screw 3 so as to fix the knife S to the pedestal body 1. Accordingly, the cutting blade Sa of the knife S and a rotary roller 5 are made into contact with an upper grinding wheel surface T so that the cutting blade Sa is polished with a angle larger than the front end angle (a). Thereby it is possible to polish the knife so that this polishing angle is larger than the set front end angle (a) by about ten degrees.