Plasma processing apparatus

A plasma processing apparatus includes an external circuit electrically connected through a line to an electrical component in a processing chamber and a filter provided on the line to attenuate or block noise introduced into the line from the electrical component toward the external circuit. The filter includes a coil having constant diameter and coil length; a tubular outer conductor accommodating the coil and forming a distributed constant line in which parallel resonance occurs at multiple frequencies in combination with the coil; and a movable member for changing each winding gap of the coil and provided in an effective section where a specific one or a plurality of parallel resonance frequencies is shifted to a higher frequency side or a lower frequency side in frequency-impedance characteristics of the filter by changing the winding gap of the coil in the effective section in a longitudinal direction of the coil.