A polishing composition comprising an abrasive, said abrasive consisting of silica grains, the average secondary particle diameter D P2 of the silica grains being from 20 nm to 100 nm, measured on an aqueous dispersion of the silica grains by dynamic light scattering, a water-soluble polymer comprising a vinyl alcohol unit, and water, the polishing composition exhibiting an etching rate of 2.0 nm/min or lower based on the following etching rate measurement: an etching rate measuring reagent LE is obtained, comprising 0.18 % by mass of the water-soluble polymer and 1.3 % by mass of ammonia with the rest being water; a silicon substrate (in a 6 cm long by 3 cm wide by 775 μm thick rectangle) is obtained, from which surface natural oxide film is removed, and its mass W0 is measured; the silicon substrate is immersed in the reagent LE at room temperature for 12 hours; the silicon substrate is removed from the reagent LE and cleaned at room temperature for 10 seconds with a cleaning solution formed of NH 3 (29%)/H 2 O 2 (31%)/ultrapure water = 1/1/8 (volume ratio); the cleaned silicon substrate is measured for its mass W1; and from the difference between the W0 and W1 as well as the specific gravity of the silicon substrate, the etching rate (nm/min) is determined; and having an abrasive adsorption of 20 % or lower based on the following abrasive adsorption measurement: the polishing composition is centrifuged to precipitate the abrasive and the resulting supernatant is subjected to measurement of total organic carbon to determine the total amount of organic carbon, C1, in the supernatant; a test solution L0 is obtained having the same composition as that of the polishing composition but without the abrasive, and the test solution L0 is subjected to measurement of total organic carbon to determine the total amount of organic carbon, C0, in the test solution L0; and from the C0 and C1, the abrasive adsorption is determined by the following equation: Abrasive adsorption % = C 0 − C 1 / C 0 × 100. an abrasive, said abrasive consisting of silica grains, the average secondary particle diameter D P2 of the silica grains being from 20 nm to 100 nm, measured on an aqueous dispersion of the silica grains by dynamic light scattering, a water-soluble polymer comprising a vinyl alcohol unit, and water, exhibiting an etching rate of 2.0 nm/min or lower based on the following etching rate measurement: an etching rate measuring reagent LE is obtained, comprising 0.18 % by mass of the water-soluble polymer and 1.3 % by mass of ammonia with the rest being water; a silicon substrate (in a 6 cm long by 3 cm wide by 775 μm thick rectangle) is obtained, from which surface natural oxide film is removed, and its mass W0 is measured; the silicon substrate is immersed in the reagent LE at room temperature for 12 hours; the silicon substrate is removed from the reagent LE and cleaned at room temperature for 10 seconds with a cleaning solution formed of NH 3 (29%)/H 2 O 2 (31%)/ultrapure water = 1/1/8 (volume ratio); the cleaned silicon substrate is measured for its mass W1; and from the difference between the W0 and W1 as well as the specific gravity of the silicon substrate, the etching rate (nm/min) is determined; and an etching rate measuring reagent LE is obtained, comprising 0.18 % by mass of the water-soluble polymer and 1.3 % by mass of ammonia with the rest being water; a silicon substrate (in a 6 cm long by 3 cm wide by 775 μm thick rectangle) is obtained, from which surface natural oxide film is removed, and its mass W0 is measured; the silicon substrate is immersed in the reagent LE at room temperature for 12 hours; the silicon substrate is removed from the reagent LE and cleaned at room temperature for 10 seconds with a cleaning solution formed of NH 3 (29%)/H 2 O 2 (31%)/ultrapure water = 1/1/8 (volume ratio); the cleaned silicon substrate is measured for its mass W1; and from the difference between the W0 and W1 as well as the specific gravity of the silicon substrate, the etching rate (nm/min) is determined; and having an abrasive adsorption of 20 % or lower based on the following abrasive adsorption measurement: the polishing composition is centrifuged to precipitate the abrasive and the resulting supernatant is subjected to measurement of total organic carbon to determine the total amount of organic carbon, C1, in the supernatant; a test solution L0 is obtained having the same composition as that of the polishing composition but without the abrasive, and the test solution L0 is subjected to measurement of total organic carbon to determine the total amount of organic carbon, C0, in the test solution L0; and from the C0 and C1, the abrasive adsorption is determined by the following equation: Abrasive adsorption % = C 0 − C 1 / C 0 × 100. the polishing composition is centrifuged to precipitate the abrasive and the resulting supernatant is subjected to measurement of total organic carbon to determine the total amount of organic carbon, C1, in the supernatant; a test solution L0 is obtained having the same composition as that of the polishing composition but without the abrasive, and the test solution L0 is subjected to measurement of total organic carbon to determine the total amount of organic carbon, C0, in the test solution L0; and from the C0 and C1, the abrasive adsorption is determined by the following equation: Abrasive adsorption % = C 0 − C 1 / C 0 × 100.