A clutter reduction effect using adaptive beam forming is uniformly obtained with respect to the entire image even in an imaging condition in which the number of bundled signals is greatly distributed in an ultrasonic image. A received signal processing unit includes a summing unit that bundles the plurality of received signals for a predetermined imaging point or a plurality of signals obtained by processing the received signals, and a weighting unit that obtains a coherence value among the plurality of signals summed in the summing unit, and weights the plurality of signals before being summed in the summing unit or a signal obtained through summing in the summing unit, with a weight corresponding to the coherence value. The weighting unit weights the coherence value nonlinearly in a predetermined direction in the subject, and weights the plurality of signals before being summed in the summing unit or the signal obtained through summing in the summing unit by using the nonlinearly weighted coherence value.
