Disclosed is a chemically amplified positive resist composition which comprises (A) a compound which contains at least one group selected among tert-alkyl ester groups and tert-alkyl carbonate groups and is capable of increasing solubility of the compound in an alkali aqueous solution by the action of an acid, (B) a compound which contains at least one group selected among acetal groups and silyl ether groups and is capable of increasing solubility of the compound in an alkali aqueous solution by the action of an acid, (C) a compound which is capable of generating an acid by irradiation with an active ray or radiation, and (D) an organic basic compound. The resist composition has high resolving power and forms a satisfactory pattern free from undergoing sensitivity decrease, T-top formation, and change in line width which are caused from exposure to post exposure bake.