The present invention images a heartbeat strength representing the strength of pulsations (beats) on a map as a new dynamics index different from the conventional waveform numerical value. A computation section according to the present invention obtains, from time-course changes of the blood flow map obtained as a result of computation of blood flow speed, a signal intensity at a fundamental frequency determined from time-series blood flow data within a predetermined region, and calculates a heartbeat strength which represents the strength of heartbeats on the basis of the signal intensity. A display section images and displays the heartbeat strength calculated by the heartbeat strength computation section. Also, the display section displays the heartbeat strength calculated by the heartbeat strength computation section by superimposing the heartbeat strength on a combined map created by averaging a plurality of blood flow maps arranged in a chronological order.
