An ultrasound signal processing device including a transmitter, a receiver, an observation point setter, and a frame generator. The transmitter repeatedly performs a transmission event, changing a position of a transducer array for each transmission event, the transmission event including selecting the transducer array from transducers on an ultrasound probe and outputting a drive signal driving the transducer array to transmit focused transmitted ultrasound. The receiver receives signals from the ultrasound probe to generate signal sequences, the signals being based on reflected ultrasound acquired by the ultrasound probe. The observation point setter sets observation points corresponding to positions in the subject. The frame generator generates a frame acoustic line signal based on the signal sequences corresponding to each of the observation points. The observation points are set such that observation points in a region shallower than a focal region each correspond to only one transmission event.
