Filter device

A filter device comprising:

• a filter case having a tubular shape and comprising an opening at an upper end or a lower end of the filter case, with an other end being covered;
• a head made of metal and provided in the filter case to cover the opening;
• a filtration member having a tubular shape and provided in an internal space formed by the filter case and the head;
• a plate made of metal and provided near the opening of the filter case;
• an IC tag provided between the filtration member and the plate;
• and
• an antenna unit provided in the head and provided with an antenna section comprising an antenna configured to communicate with the IC tag, wherein
• the antenna unit comprises a case having a rod shape and inserted into the head,
• the antenna section is provided at a first end corresponding to one end of the case,
• the case is provided in the head such that the antenna section is exposed when the head is viewed from a side of the filter case,
• the plate is provided with an aperture from which the IC tag is exposed,
• the IC tag has a hollow disk shape,
• the plate is provided with a plurality of the apertures, and
• centers of the plurality of apertures are evenly arranged along a circle centered at a center axis of the filter case and having a diameter larger than an inner diameter of the IC tag and smaller than an outer diameter of the IC tag.