Ultrasound signal processing device performing transmission events of transmitting converging ultrasound beams to subject using ultrasound probe having transducer elements, receiving ultrasound reflection from the subject, generating acoustic line signal, and including ultrasound signal processing circuitry configured to operate as: transmitter varying focal point defining position where ultrasound beams converge between transmission events and performing each transmission event； receiver generating, for each transmission event, receive signal sequences for the transducer elements based on ultrasound reflection； and delay-and-sum calculator generating acoustic line signal for each measurement point by performing processing for specifying measurement point signal for each transmission event and performing weighted delay-and-summing of measurement point signals for the transmission events, the processing including identification of transducer element on straight line passing through the measurement point and the focal point and specification of, as the measurement point signal, receive signal for the transducer element from the sequence for the transducer element.
