In the plasma processing apparatus of the present invention, a first electrode for connecting a high frequency electric power source in a chamber is arranged to be opposed to a second electrode. A substrate (W) to be processed is placed between the electrodes. There is provided a harmonic absorbing member for being able to absorb harmonics of the high frequency electric power source so as to come in contact with a peripheral portion or circumference of a face of the first electrode 21, which is opposite the second electrode. The harmonic absorbing member absorbs the reflected harmonic before the harmonic returns to the high frequency electric power source. By absorbing the harmonic in this manner, the standing wave due to the harmonic will be effectively prevented from being generated, and the density of plasma is made even.