Polishing composition

A polishing composition comprising a copolymer, water and an abrasive,

• wherein the copolymer has a constitutional unit expressed as the following formula (I) and at least one constitutional unit selected from the group consisting of constitutional units expressed as the following formulas (II) to (III):
• wherein in the formula (I), R1 is a hydrogen atom or a methyl group, R2 is a C1 to C4 alkyl group, AO is a C1 to C8 oxyalkylene group, p is 0 or 1, n is an average number of total AO units added and ranges from 6 to 300, and the proportion of an oxyethylene group in (AO)n is 80 mol % or more;
• in the formula (II), R3 is a hydrogen atom or a methyl group, X is an oxygen atom or an NH group, and R4 is a C4 to C30 alkyl group or a C6 to C30 aryl group;
• and
• in the formula (III), R5 is a hydrogen atom or a methyl group, R6 is a hydrogen atom or a C1 to C3 alkyl group, AO is a C2 to C4 oxyalkylene group, m is an average number of total AO units added and ranges from 3 to 150, and the proportion of an oxypropylene group and an oxybutylene group in (AO)m is 80 mol % or more,
• wherein the content of water in the polishing composition is 75 wt % or more, and the content of the copolymer in the polishing composition is 0.001 to 3 wt %.