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 (a0) represented by general formula (a0) shown below and a structural unit (a1) derived from an acrylate ester having a polycyclic group-containing, acid dissociable, dissolution inhibiting group of a tertiary alkyl ester-type: wherein: R represents a hydrogen atom, a halogen atom, a lower alkyl group or a halogenated lower alkyl group; Y1 represents an aliphatic cyclic group; Z represents a tertiary alkyl group-containing group; a represents an integer of 1 to 3, and b represents an integer of 0 to 2, such that a+b=1 to 3; and each of c, d and e independently represents an integer of 0 to 3.