In a weather radar apparatus, an array antenna (11) includes antenna elements arranged in a horizontal direction and an elevation angle direction to radiate transmission waves into space and receive reflected waves which are the transmission waves reflected from space. An antenna driver (15) rotates the array antenna (11) in an azimuth direction. A transmitter (12) controls the antenna elements to radiate the transmission waves with controlled amplitudes and phases respectively so as to form a transmission fan beam extending in the azimuth direction. A reception beam former (18) processes reception signals generated by the antenna elements from the reflected waves so as to form a plurality of reception beams in the azimuth direction. A reception beam allocator (19) receives an azimuth at which the array antenna (11) is oriented, and allocates the reception beams to respective azimuth ranges which are predetermined ranges of azimuth. A weather observer (21) obtains information about a result of weather observation for each of the azimuth ranges, from the reception beams allocated to the respective azimuth ranges by the reception beam allocator (19).