To provide abrasive grain which is not only excellent in rigidity, wear resistance, and cleaving performance but also firmly fixed to a bonding agent, and to provide a grindstone using the abrasive grain, which is proof against separation of the abrasive grain from the bonding agent, and suitable for highly efficient grinding.

The abrasive grain 10 has a smooth surface 11 which has a surface roughness of Ra 0.01 to 0.05 μm and makes up at least 30% of the entire surface area, and a rough surface 12 which has a surface roughness of Ra 0.06 to 0.20 μm and makes up at least 30% of the entire surface area. The grindstone is formed of the abrasive grain 10 and the binding agent. The abrasive grain 10 is formed of CBN (cubic boron nitride), and has the smooth surface 11 which has a surface roughness of Ra 0.01 to 0.05 μm and makes up at least 30% of the entire surface area, and the rough surface 12 which has a surface roughness of Ra 0.06 to 0.20 μm and makes up at least 30% of the entire surface area. The binding agent is formed of a vitrified bond.