To provide a CMP abrasive which can polish a silicon oxide film at a high speed without leaving polishing scratches, and a polishing method of a substrate.

In this polishing method of the substrate, a CMP abrasive for semiconductors comprising cerium oxide particles, a dispersant and water and the substrate on which a film to be polished is formed are pressed onto a polishing cloth of a polishing platen, and feeding the CMP abrasive to the clearance between the polished film and the polishing cloth, the film to be polished is polished by moving the substrate and the polishing platen relatively.