A reception beamformer 140 includes a delay-and-sum unit 142 that performs delay-and-sum processing with respect to reception signal sequences from multiple channels based on reflected ultrasound to calculate acoustic line signal line data. The delay-and-sum unit 142, in first reception beamforming processing, synthesizes the acoustic line signal line data calculated in the delay-and-sum processing by summing acoustic line signals associated with the observation points having the same positions, and, in the second reception beamforming processing, outputs the acoustic line signal data calculated in the delay-and-sum processing as is. Time taken by the delay-and-sum unit 142 to generate the acoustic line signal line data per set of acoustic line signal line data is equal or approximately equal in the first reception beamforming processing and the second reception beamforming processing.
