A composition for forming a resist underlayer film that enables the formation of a desired resist pattern; and a method for producing a resist pattern and a method for producing a semiconductor device, each of which uses the composition for forming a resist underlayer film. (In formula (1), A1, A2, A3, A4, A5, and A6 each independently represent a hydrogen atom, methyl group, or ethyl group; Q1 represents a divalent organic group; R1 represents a tetravalent organic group; and R2 represents an alkenyl group or alkynyl group having 2-10 carbon atoms.) The film-forming composition contains a solvent and a polymer that has a unit structure given by formula (1).