A resist underlayer film-forming composition includes a polymer including a structural unit shown by a formula (1), and having a polystyrene-reduced weight average molecular weight of from 3000 to 10000, and a solvent. Each of R3 to R8 independently represents a group shown by a formula (2), a hydrogen atom, a hydroxyl group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkoxycarbonyl group having 2 to 10 carbon atoms, an aryl group having 6 to 14 carbon atoms, or a glycidyl ether group having 3 to 6 carbon atoms, wherein at least one of R3 to R8 represents the group shown by the formula (2).