An object of the present invention is to provide a polymer used for a resist composition having high absorption efficiency for a particle beam or an electromagnetic wave, and excellence in sensitivity, resolution and pattern performance characteristics, and provide a resist composition containing the polymer and a method of manufacturing a device using thereof.The polymer comprises: a unit A; and a unit B, wherein the unit A has an onium salt structure and generates a first radical by irradiation with a particle beam or an electromagnetic wave, the unit B has a radical generating structure containing at least one multiple bond which is between a carbon atom and a carbon atom or between a carbon atom and a heteroatom, and generates a second radical by irradiation with a particle beam or an electromagnetic wave, and the multiple bond is not one contained in a benzenoid aromatic.