To provide an air filter capable of surely sterilizing with a simple constitution.

The air filter has a first electrode constituted by forming a metal into a grid, a plate which keeps one side face in contact with the first electrode and has a predetermined thickness and through holes penetrating through in a thickness direction, a second electrode which contacts the face of the plate different from the first electrode and which is constituted by forming a metal into a grid, and a power source section applying a predetermined voltage across the first electrode and the second electrode.