A composition for forming a silicon-containing resist underlayer film, wherein the composition contains: a component comprising at least one or more compounds selected from the group consisting of a polymer having repeating units shown by the following general formulae and and being capable of generating a phenolic hydroxyl group, a hydrolysate of the polymer, and a hydrolysis-condensate of the polymer, and a component which is a silicon-containing compound obtained by hydrolysis-condensation of a mixture containing, at least, one or more hydrolysable silicon compounds represented by the following general formula and one or more hydrolysable silicon compounds represented by the following general formula, wherein R 1 represents an organic group having 1 to 20 carbon atoms or a hydroxyl group, R 2 represents an acid-labile group, and n1 and n2 satisfy 0≤n1≤3, 1≤n2≤3, and 1≤n1+n2≤5; R 3 represents a hydrogen atom or a methyl group, and R 4 represents a single bond or a divalent organic group having 1 to 20 carbon atoms; R 5 represents a hydrogen atom or an organic group having 1 to 30 carbon atoms, R 6 represents an alkyl group having 1 to 6 carbon atoms, R 7 represents a hydrogen atom or a methyl group, R 8 represents a single bond or a divalent organic group having 1 to 20 carbon atoms, and "n" satisfies 0≤n≤2; and m1 and m2 represent molar ratios of the foregoing repeating units in the foregoing polymer and satisfy 0<m1<1, 0<m2<1, and 0<m1+m2≤1, R 11 m11 R 12 m12 R 13 m13 Si (OR 14) (4-m11-m12-m13) wherein R 14 represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and each of R 11, R 12, and R 13 represents a hydrogen atom or a monovalent organic group having 1 to 30 carbon atoms; m11, m12, and m13 represent 0 or 1 and satisfy 1≤m11+m12+m13≤3, Si(OR 15) 4 wherein R 15 represents an alkyl group having 1 to 6 carbon atoms. a component comprising at least one or more compounds selected from the group consisting of a polymer having repeating units shown by the following general formulae and and being capable of generating a phenolic hydroxyl group, a hydrolysate of the polymer, and a hydrolysis-condensate of the polymer, and a component which is a silicon-containing compound obtained by hydrolysis-condensation of a mixture containing, at least, one or more hydrolysable silicon compounds represented by the following general formula and one or more hydrolysable silicon compounds represented by the following general formula, wherein R 1 represents an organic group having 1 to 20 carbon atoms or a hydroxyl group, R 2 represents an acid-labile group, and n1 and n2 satisfy 0≤n1≤3, 1≤n2≤3, and 1≤n1+n2≤5; R 3 represents a hydrogen atom or a methyl group, and R 4 represents a single bond or a divalent organic group having 1 to 20 carbon atoms; R 5 represents a hydrogen atom or an organic group having 1 to 30 carbon atoms, R 6 represents an alkyl group having 1 to 6 carbon atoms, R 7 represents a hydrogen atom or a methyl group, R 8 represents a single bond or a divalent organic group having 1 to 20 carbon atoms, and "n" satisfies 0≤n≤2; and m1 and m2 represent molar ratios of the foregoing repeating units in the foregoing polymer and satisfy 0<m1<1, 0<m2<1, and 0<m1+m2≤1, R 11 m11 R 12 m12 R 13 m13 Si (OR 14) (4-m11-m12-m13) wherein R 14 represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and each of R 11, R 12, and R 13 represents a hydrogen atom or a monovalent organic group having 1 to 30 carbon atoms; m11, m12, and m13 represent 0 or 1 and satisfy 1≤m11+m12+m13≤3, Si(OR 15) 4 wherein R 15 represents an alkyl group having 1 to 6 carbon atoms.