The present invention relates to a method for measuring radical species distribution in plasma by determining the intensity of the light emitted from the radical species and plasma parameters in plasma with the aid of optical and electrostatic probes, and an apparatus for measuring the radical species distribution. The method of the invention comprises the steps of: (i) measuring integral light intensity in a vacuum container by an optical probe inserted to the vacuum container; (ii) determining light intensity at each point of the vacuum container by differentiating the integral light intensity; (iii) measuring current and voltage applied to the electrostatic probe in the vacuum container; (iv) determining plasma parameters from the measured current and voltage; and, (v) measuring distribution of radical species from the light intensity and plasma parameters.