An optimum application voltage for reducing deposits on a peripheral portion of a substrate as well as improving a process result in balance is effectively found without changing a height of a focus ring. A plasma processing apparatus includes a focus ring which includes a dielectric ring provided so as to surround a substrate mounting portion of a mounting table and a conductive ring provided on the dielectric ring; a voltage sensor configured to detect a floating voltage of the conductive ring; a DC power supply configured to apply a DC voltage to the conductive ring. An optimum voltage to be applied to the conductive ring is obtained based on a floating voltage actually detected from the conductive ring, and the optimum application voltage is adjusted based on a variation in the actually detected floating voltage for each plasma process.