A composition for forming a resist underlayer film includes a polysiloxane, and a solvent composition. The solvent composition includes an organic solvent which includes a compound represented by the following formula (1) or a carbonate compound and which has a standard boiling point of no less than 150.0° C. R1 and R2 each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms or an acyl group having 1 to 4 carbon atoms. R3 represents a hydrogen atom or a methyl group. n is an integer of 1 to 4. In a case where n is no less than 2, a plurality of R3s are identical or different.