There is disclosed a polymer containing at least a repeating unit represented by the following general formula (1), and the resist composition containing the polymer as a base resin, especially a chemically amplified resist composition. There can be provided a resist composition which has etching resistance in a practical use level, and is excellent in an adhesion property with a substrate and an affinity with a developer, and has a sensitivity and resolving power which is far excellent compared with a conventional one, wherein swelling is small at the time of development, especially for photolithography which uses a high-energy beam as a light source, and especially be provided a chemically amplified resist composition ##STR00001##