The present invention provides a polishing fluid composition which can effectively polish a surface of a semiconductor silicon wafer or a surface of a film comprising silicon to be formed on silicon wafers with a markedly reduced amount of colloidal silica to be used as abrasives, or a polishing fluid composition which is particularly useful for a polishing step after removal of an oxide layer in a two-step polishing method. The former polishing fluid composition comprises an alkaline suspension which contains a water-soluble silicic acid component, colloidal silica and an alkaline component, and which has a pH value of 8.5 to 13. Meanwhile, the latter polishing fluid composition comprises an alkaline solution which contains a water-soluble silicic acid component and an alkaline component, and which has a pH value of 8.5 to 13; and is substantially free of abrasive particles.