Antenna device

An antenna device comprising:

• a ground plate made of a conductor with a flat plate shape;
• an opposing conductive plate made of another conductor with a flat plate shape, arranged to space apart from the ground plate by a predetermined distance, and having a power supply point electrically connected to a power supply line;
• a short-circuit portion electrically connecting the opposing conductive plate and the ground plate;
• and
• a radio wave shield body for shielding a propagation of an electric field, which is arranged on an upper side of the opposing conductive plate and is made of a conductor or a dielectric material, wherein:
• parallel resonance at a predetermined target frequency is generated by an inductance provided in the short-circuit portion and a capacitance between the ground plate and the opposing conductive plate;
• and
• the radio wave shield body is arranged so as to contact with an upper surface of an edge portion of the opposing conductive plate.