A device for measuring a polarization direction of a linearly polarized received wave with circularly polarized antennas includes an intensity ratio providing unit that provides, to the antennas, intensity ratios different depending on an arrival direction for the received wave; a storage unit that stores a first table in which an intensity ratio of a vertically polarized component of the received wave between two of the antennas is associated with the arrival direction and a second table in which an intensity ratio of a horizontally polarized component of the received wave between the two antennas is associated with the arrival direction; a detector that acquires an intensity ratio of the received wave; an acquiring unit that acquires the arrival direction; and an arithmetic unit that calculates the polarization direction of the received wave based on the acquired intensity ratio and the intensity ratios of the vertically and horizontally polarized components.