An evaluation value calculation unit (50) evaluates a degree of phasing on the basis of a plurality of received-wave signals obtained from a delay processing unit (30) to thereby calculate a two-dimensional evaluation value related to a two-dimensional array of a plurality of oscillating elements (12). The evaluation value calculation unit (50) obtains a two-dimensional evaluation value of an xy plane from a one-dimensional evaluation value in the x direction and a one-dimensional evaluation value in the y direction. A multiplication unit (60) multiplies the two-dimensional evaluation value and the received beam outputted from an addition processing unit (40) to adjust the gain of the received beam. Unnecessary signal components are thereby reduced.
