A positive resist composition comprises: (A) a resin capable of increasing its solubility in an alkali developer by action of an acid and not containing a silicon atom; (B) a compound capable of generating an acid upon irradiation with actinic ray or radiation, (C) a silicon atom-containing resin having at least one group selected from groups (X) to (Z), (X) an alkali-soluble group, (Y) a group capable of decomposing by action of an alkali developer to increase the solubility of resin (C) in an alkali developer, (Z) a group capable of decomposing by action of an acid to increase the solubility of resin (C) in an alkali developer; and (D) a solvent.