To easily and surely polish kitchen knives having different cutting blade angles, by providing a guide means which can adjust an inclination angle with respect to a diamond wheel, for guiding a cutter such as a kitchen knife.

When a kitchen knife 31 is polished, the inclination of guides 6 are adjusted in accordance with a cutting blade angle after screws 8 are loosened, and accordingly, the angle between the guide 6 and a diamond wheel 4 is adjusted to the cutting blade angle of the kitchen knife 31. Further, a button 3 is pushed so as to start a motor for rotating the diamond wheel. In this condition, the kitchen knife 31 is made into contact with one of the guides 6, and then the kitchen knife is depressed along the guide 6 until its cutting blade is locked to front and rear stoppers 6a. The cutting blade is stopped by the stopper 6a, and the cutting blade between the stoppers is made into contact with the diamond wheel 4. Subsequently, the cutting blade is polished. After completion of polishing, the cutting blade is polished on the other side as necessary.