Abstract: The present disclosure relates to a method of controlling a plasma processing apparatus, and a plasma processing apparatus for performing the method. According to one embodiment of the present disclosure, a method of controlling a plasma processing apparatus includes supplying power having a sine wave from a high-frequency power source to a lower electrode to generate a plasma; and supplying power from the high-frequency power source to the lower electrode, to control an ion in the generated plasma, and when a voltage of a wafer disposed on the lower electrode has a negative peak value in a phase region, inputting a negative DC voltage to a focusing ring by a DC power source.