According to one embodiment, an antenna device includes a first transmission array antenna including transmission antennas of a first number, arranged with a first distance in a first direction, a first reception array antenna including reception antennas of a second number, arranged with a second distance in a first direction or a second direction which is parallel to the first direction, a second transmission array antenna including transmission antennas of a third number, arranged with the first distance in the first direction, and a second reception array antenna including reception antennas of a fourth number, arranged with the second distance in the first direction or the second direction.