A positive resist composition including a resin component (A) which exhibits increased alkali solubility under action of acid and an acid-generator component (B) which generates acid upon exposure, the resin component (A) including a structural unit (a1) derived from an acrylate ester having a tertiary alkyl ester-type acid dissociable, dissolution inhibiting group containing an aliphatic monocyclic group and/or an aliphatic branched, tertiary alkyl ester-type acid dissociable, dissolution inhibiting group, and the acid-generator component (B) including an acid generator (B1) having a cation moiety represented by general formula (b′-1) shown below: wherein each of R1 and R2 independently represents a naphthyl group which may have a substituent; and R3 represents an alkyl group or an aryl group exclusive of a naphthyl group.