A resin composition for forming a phase-separated structure, including a block copolymer, and an ion liquid containing a compound having a cation moiety and an anion moiety, the anion moiety being represented by general formula (a1), (a2) or (a3), in which X″ represents an alkylene group of 2 to 6 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom; Y″ and Z″ each independently represents an alkyl group of 1 to 10 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom; R″ represents an alkyl group of 1 to 5 carbon atoms in which at least one hydrogen atom is optionally substituted with a fluorine atom, m represents an integer of 1 to 6, and n represents an integer of 0 to 5, provided that m+n=6.