A positive resist composition including a base component (A) which exhibits increased solubility in an alkali developing solution under action of acid and an acid-generator component (B) which generates acid upon exposure, the base component (A) including a polymeric compound (A1) having a structural unit (a0-1) represented by general formula (a0-1) (wherein R1 represents a hydrogen atom, a lower alkyl group or a halogenated lower alkyl group; R8 represents a divalent linking group; and R7 represents an acid dissociable, dissolution inhibiting group) and a structural unit (a0-2) represented by general formula (a0-2) (wherein R3 represents a hydrogen atom, a lower alkyl group or a halogenated lower alkyl group; R4 represents a branched alkyl group of 3 or more carbon atoms; and each of R5 and R6 independently represents an alkyl group, wherein R5 and R6 are mutually bonded to form a ring).