A linear-depolarization ratio calculator (12) is configured so as to determine a radar reflectivity factor Zhh in transmission of a horizontally polarized wave and reception of a horizontally polarized wave, the radar reflectivity factor being a reflected wave intensity after integration of a reflected wave intensity Vhh(n) calculated by a reflected-wave intensity calculator (11), and a radar reflectivity factor Zvh in transmission of a horizontally polarized wave and reception of a vertically polarized wave, the radar reflectivity factor being a reflected wave intensity after integration of a reflected wave intensity Vvh(n+2) and calculate a linear depolarization ratio LDRvh which is the ratio between the radar reflectivity factor Zhh and the radar reflectivity factor Zvh. As a result, even when three types of polarized-wave transmission/reception processing elements are repeatedly performed, the linear depolarization ratio LDRvh can be calculated.