An ultrasound signal processing device including: a transmitter performing transmission events while varying ultrasound beam travel direction； a reception processor generating an acoustic line signal for each transmission event that is performed by generating reception signal sequences and performing delay-and-summing； a combiner generating an intermediate combined acoustic line signal by combining acoustic line signals corresponding to the first to latest transmission events performed for a current frame； an evaluator judging whether a subsequent transmission event is to be performed for the current frame by calculating an evaluation value from an energy value of the intermediate combined acoustic line signal and judging whether the evaluation value satisfies a predetermined condition； and an outputter outputting the intermediate combined acoustic line signal as a combined acoustic line signal once the evaluator judges that a subsequent transmission event is not to be performed for the current frame.
