The present invention relates to a polishing composition that can be preferably used to polish a silicon wafer. The polishing composition includes a block polyether represented by the chemical formula HO--(EO).sub.a--(PO).sub.b--(EO).sub.c--H, wherein EO represents an oxyethylene group, PO represents an oxypropylene group, each of a and c represents the polymerization degree of ethylene oxide, b represents the polymerization degree of propylene oxide, and each of a, b, and c is an integer of 1 or greater; silicon dioxide; a basic compound; at least either one of hydroxyethyl cellulose and polyvinyl alcohol; and water.