ANTENNA DEVICE

PROBLEM TO BE SOLVED: To secure the size of an antenna plane, also sufficiently secure the size of a metallic board comparing with the size of the antenna plane and also to avoid an ambient metallic influence on radiated radio waves by arranging an antenna element obliquely with respect to a housing storing a radio device. SOLUTION: A conductive housing 1 has a hexahedral shape whose bottom is opened and one conductive plane 1a that constitutes the housing 1 is tilted obliquely with respect to the other plane. An inclination angle θ of the plane 1a against the housing 1 sets an antenna plane 10 and the angle θ of the plane 1a so that a metallic body, dielectric or a magnetic body other than what forms an antenna device can not exist in an area side that includes the plane 10 between two space areas which are divided by virtually and limitlessly extending the plane 10. Thus, it is possible to transmit radio waves while reducing the influence of ambient metallic pipe arrangement even when the antenna device is installed in limited space around a gas meter, etc.