An ultrasonic signal processing device that performs speed analysis by a color flow mapping method by executing ultrasonic transmission/reception to/from a subject by driving a plurality of transducers arranged in array on an ultrasonic probe, includes: a transmitter that repeatedly executes a process of selecting two or more transmission conditions in predetermined order and transmitting an ultrasonic wave prescribed under the selected transmission condition into the subject； a reception beam former that generates an acoustic line signal on the basis of a reflected ultrasonic wave in synchronization with the ultrasonic transmission by the transmitter； a quadrature detector that performs quadrature detection on the acoustic line signal to generate a complex acoustic line signal； and a speed calculator that performs a process of grouping a plurality of complex acoustic line signals as a packet for each transmission condition and analyzes per packet to generate speed information in the subject.
