A filtering medium includes a nonwoven fabric and a first electrode having an input terminal of power. The first electrode is provided on a surface of the nonwoven fabric. Alternatively, in a case where the nonwoven fabric has a plurality of fiber layers, the first electrode may be provided between the fiber layers. An air purifier includes the filtering medium disposed between a sucker and a discharger of a gas, and an output terminal via which power is output to the first electrode of the filtering medium.