Provided are a polishing composition having excellent dissolution stability and enabling a polishing process at a high polishing rate, and a polishing method using the same. The polishing composition comprises: component (A) which is composed of one or more kinds of abrasive grains selected from diamond, boron nitride, boron carbide and silicon carbide; component (B) which is composed of a fatty acid having 10 to 22 carbon atoms; component (C) which is composed of a nonionic surfactant; component (D) which is composed of an organic amine compound; and component (E) which is composed of a dispersion medium. The average particle size of the abrasive grains of the component (A) is greater than 1.0 m and smaller than or equal to 10.0 m, the content of the component (C) is 0.3 to 10 wt%, and the mole ratio of the component (D) to the component (B) [(D)/(B)] is 45/55 to 90/10. The polishing method is to polish a substrate including one or more kinds of materials selected from sapphire, silicon carbide, gallium nitride and aluminum nitride by using the polishing composition described above.