To easily mount a grinding stone in a holder and demount it therefrom by a simple structure, in the grinding stone integrally formed with many abrasive grains by a binding agent.

In this grinding stone 10 for polishing connecting many abrasive grains by a binding agent to be integrally formed therewith, powder consisting of magnetic material is included in the binding agent. A magnet 14 is provided in a side of a holder 12, so as to hold by its magnetic force a magnet total unit attracted capable of mounting/demounting to the side of the holder 12.