A positive resist composition comprises (A) a resin component which becomes soluble in an alkaline developer under the action of an acid, and (B) an acid generator. The resin (A) is a polymer comprising tertiary alkyl protective group units having a hydrophobic tetracyclo[4.4.0.1.sup.2,5.1.sup.7,10]-dodecane structure, hydroxyadamantane units, monocyclic lactone units, and carboxylic acid units. The acid generator (B) is a specific sulfonium salt compound.