The present invention provides a polishing liquid composition for a magnetic disk substrate that can reduce residual inorganic particles and scratches without loss of productivity and a method of producing a magnetic disk substrate using the polishing liquid composition. The polishing liquid composition contains inorganic particles, a diallylamine polymer, an acid and water, the diallylamine polymer includes one or more constitutional units selected from those represented by the following general formulas (I-a), (I-b), (I-c) and (I-d), and the content of the diallylamine polymer in the polishing liquid composition is 0.008 to 0.100 wt %