An antenna device comprising: a cavity composed of a metal conductor having an opening closed in a bottom; a first excitation circuit superposed and disposed on an upper surface of the cavity, including inside thereof a first power feeding probe and a first transmission line that feeds electric power to the first power feeding probe, and radiating a radio wave of a first polarized wave; and a radiator superposed and disposed on an upper surface of the first excitation circuit, and composed of a metal conductor having an open hole, the antenna device further comprising: a first matching element composed of a conductor above the first excitation circuit; and between the first excitation circuit and the radiator, a second excitation circuit including inside thereof a second power feeding probe and a second transmission line that feeds electric power to the second power feeding probe, and radiating a radio wave of a second polarized wave orthogonal to the first polarized wave; wherein the first matching element has a characteristic of matching a polarized wave excited by the first excitation circuit, and transmitting a polarized wave excited by the second exciting circuit, and the antenna device further includes, above the second excitation circuit, a second matching element matching a polarized wave excited by the second excitation circuit, and transmitting the polarized wave excited by the first excitation circuit; characterized in that the first matching element is a slit parallel to the polarized wave excited by the first excitation circuit, and the second matching element is a slit parallel to the polarized wave excited by the second excitation circuit. a cavity composed of a metal conductor having an opening closed in a bottom; a first excitation circuit superposed and disposed on an upper surface of the cavity, including inside thereof a first power feeding probe and a first transmission line that feeds electric power to the first power feeding probe, and radiating a radio wave of a first polarized wave; and a radiator superposed and disposed on an upper surface of the first excitation circuit, and composed of a metal conductor having an open hole, the antenna device further comprising: a first matching element composed of a conductor above the first excitation circuit; and between the first excitation circuit and the radiator, a second excitation circuit including inside thereof a second power feeding probe and a second transmission line that feeds electric power to the second power feeding probe, and radiating a radio wave of a second polarized wave orthogonal to the first polarized wave; wherein a first matching element composed of a conductor above the first excitation circuit; and between the first excitation circuit and the radiator, a second excitation circuit including inside thereof a second power feeding probe and a second transmission line that feeds electric power to the second power feeding probe, and radiating a radio wave of a second polarized wave orthogonal to the first polarized wave; wherein the first matching element has a characteristic of matching a polarized wave excited by the first excitation circuit, and transmitting a polarized wave excited by the second exciting circuit, and the antenna device further includes, above the second excitation circuit, a second matching element matching a polarized wave excited by the second excitation circuit, and transmitting the polarized wave excited by the first excitation circuit; characterized in that the first matching element is a slit parallel to the polarized wave excited by the first excitation circuit, and the second matching element is a slit parallel to the polarized wave excited by the second excitation circuit.