A resist underlayer film material contains (A) a resin having a compound shown in the following general formula (1A), and (B) an organic solvent. Mw/Mn of the compound shown in the general formula (1A) is 1.00≤Mw/Mn≤1.25. This provides: a resist underlayer film material having all of favorable dry etching resistance, heat resistance to 500° C. or higher, and high filling and planarizing properties; and methods for forming a resist underlayer film and patterning processes which use the material.