Disclosed is a CMP slurry comprising a first colloidal particle having a primary particle diameter ranging from 5 nm to 30 nm and an average particle diameter of d1, the first colloidal particle being incorporated in an amount of w1 by weight and a second colloidal particle having a primary particle diameter larger than that of the first colloidal particle and an average particle diameter of d2, the second colloidal particle being formed of the same material as that of the first colloidal particle and incorporated in an amount of w2 by weight, wherein d1, d2, w1 and w2 are selected to concurrently meet following conditions (A) and (B) excluding situations where d1, d2, w1 and w2 concurrently meet following conditions (C) and (D): 3.ltoreq.d2/d1.ltoreq.8 (A) 0.7.ltoreq.w1/(w1+w2).ltoreq.0.97 (B) 3.ltoreq.d2/d1.ltoreq.5 (C) 0.7.ltoreq.w1/(w1+w2).ltoreq.0.9. (D)