The invention provides a composition for forming a resist underlayer film including: as a component (A), a silicon-containing compound obtained by hydrolysis and/or condensation of one or more kinds of silicon compounds represented by the following general formula (A-1). There can be provided a composition for forming a resist underlayer film having etching selectivity relative to a conventional organic film and a silicon-containing film and favorable pattern adhesiveness relative to fine pattern even in a complicated patterning process. R1Aa1R2Aa2R3Aa3Si(OR0A)(4-a1-a2-a3)  (A-1)