It is intended to provide a plasma doping method and apparatus which are superior in the controllability of the concentration of an impurity that is introduced into a surface layer of a sample.A prescribed gas is introduced into a vacuum container 1 from a gas supply apparatus 2 while being exhausted by a turbomolecular pump 3 as an exhaust apparatus. The pressure in the vacuum container 1 is kept at a prescribed value by a pressure regulating valve 4. High-frequency electric power of 13.56 MHz is supplied from a high-frequency power source 5 to a coil 8 disposed close to a dielectric window 7 which is opposed to a sample electrode 6, whereby induction-coupled plasma is generated in the vacuum container 1. A high-frequency power source 10 for supplying high-frequency electric power to the sample electrode 6 is provided. Every time a prescribed number of samples have been processed, a dummy sample is subjected to plasma doping and then to heating. The conditions for processing of a sample are controlled so that the measurement value of the surface sheet resistance becomes equal to a prescribed value, whereby the controllability of the impurity concentration can be increased.