A polishing composition of the present invention contains: a polyvinyl alcohol resin having a 1,2-diol structure in its side chain, the polyvinyl alcohol resin being a copolymer of a monomer represented by Formula (1) below and a vinyl ester monomer; an organic acid; and abrasive grains whose surfaces are chemically modified so as to have a minus zeta potential on the surfaces in a solution with a pH of 2.0 or more and to have no isoelectric point: (where R1 to R6 each independently denote a hydrogen atom or an organic group, X denotes a single bond or a linking group, and R7 and R8 each independently denote a hydrogen atom or R9—CO— (where R9 denotes an alkyl group)).