Filter device and plasma processing apparatus

A filter device comprising:

• a plurality of coils arranged coaxially;
• a plurality of wirings, each of which is electrically connected to one end of each of the coils of the plurality of coils;
• a plurality of capacitors, each of which is connected between the other end of each of the coils of the plurality of coils and the ground;
• and
• a housing electrically grounded and configured to accommodate therein the plurality of coils,
• wherein each of the wirings at least partially extends into the housing and has a length that is adjustable in the housing,
• wherein the plurality of coils form a plurality of coil groups, each of the coil groups including two or more coils;
• in each of the coil groups, the two or more coils are arranged such that winding portions of the two or more coils extend in a spiral shape around a central axis and turns of each of the winding portions are arranged sequentially and repeatedly in an axial direction in which the central axis extends;
• the coil groups are arranged coaxially with the central axis, and
• wherein the plurality of the coil groups are arranged sequentially in a radial direction relative to the central axis;
• a pitch between the turns of each of the winding portions of a first coil group of the plurality of coil groups is greater than a pitch between the turns of each of the winding portions of a second coil group of the plurality of coil groups;
• and
• the second coil group of the plurality of coil groups is provided at an inner side of the first coil group of the plurality of coil groups.