There is provided an apparatus of performing a plasma process on substrates mounted on an upper surface of a rotary table. The apparatus includes: a heater for heating the substrates; a process gas supply part for supplying a process gas toward the upper surface of the rotary table; an antenna for generating an inductively coupled plasma by converting the process gas to plasma; a light detection part for detecting respective light intensities of R, G and B component as light color components; a calculation part for obtaining an evaluation value corresponding to a change amount before and after supplying a high-frequency power to the antenna, with respect to at least one of the respective light intensities; and an ignition determination part for comparing the evaluation value with a threshold value and to determine that ignition of plasma is not generated if the evaluation value does not exceed the threshold value.