A chemical amplification type positive resist composition comprising: a resin which has a hydroxystyrene-based polymerization unit, a 3-hydroxy-1-adamantyl methacrylate-based polymerization unit and a polymerization unit having a group unstable toward an acid, and, though insoluble or hardly soluble in an alkali in itself, becomes alkali-soluble after the acid-unstable group has been cleaved by the action of an acid; and an acid generating agent is provided. This resist composition is improved in exposure latitude and resolution. Moreover, such properties as sensitivity, heat resistance, the ratio of residual thickness, coatability, and dry etching resistance are also maintained good. Thus, through the use of this composition, a fine resist pattern can be formed with high precision.