Disclosed is a plasma processing apparatus, comprising a first electrode on which an object to be processed is to be disposed, a second electrode arranged to face the first electrode, a high frequency power supply for supplying a high frequency power between the first and second electrodes, a processing gas supplying mechanism for forming a plasma into a region between the first and second electrodes, and a bias potential detecting mechanism for detecting the bias potential of the first electrode. The bias detecting mechanism has a detecting terminal positioned in the vicinity of the object to be processed.