A radical generator includes a supply tube, a plasma-generating tube, a coil winding about an outer circumference of the plasma-generating tube, for generating an inductively coupled plasma in the plasma-generating tube, an electrode for generating a capacitively coupled plasma in the plasma-generating tube and adding the capacitively coupled plasma to the inductively coupled plasma, and a parasitic-plasma-preventing tube including a dielectric material which extends from a bottom of the plasma-generating tube to an opening of the supply tube in a space between the bottom and the opening, and a tip part thereof is inserted into the supply tube to cover an inner wall of the supply tube for preventing a generation of a parasitic plasma between the electrode and the inner wall of the supply tube.