An abrasive liquid for CMP process characterized by comprising an abrasive material, an aqueous solvent and an addition agent, and containing abrasive particles having a particle diameter of 20 to 80 nm by 15 weight % or more on the basis of the weight of the abrasive liquid; and a method of polishing by using the abrasive liquid are appropriate for the processing of flattening the surface of a device wafer on which at least a silicon oxide film is formed, and take effect of being capable of stably performing superior abrasive properties such as flattening properties, low flaw properties and high washing properties, and then are the most appropriate for the processing of flattening the surface of a semiconductor device comprising a layer insulation film or an element separation film, a magnetic head and a substrate for a liquid crystal display in the semiconductor industry.