A chemically amplified positive resist composition excellent in sensitivity and resolution as well as other resist performance characteristics comprising a resin (X) which has a polymeric unit represented by the following formula (I): wherein R1 represents hydrogen or methyl, R2 and R3 represent alkyl having 1 to 4 carbon atoms, and R4 and R5 represent hydrogen, hydroxyl or alkyl, polymeric unit represented by the following formula (II): and a polymeric unit derived from unsaturated dicarboxylic acid anhydride selected from maleic anhydride and itaconic anhydride; and an acid generating agent (Y).