In one embodiment, a scanning unit (2, 3, 4) repeatedly scans an internal region of an object with an ultrasonic wave at a predetermined frame rate via an ultrasonic probe. An image generation unit (6) extracts a blood flow signal based on a Doppler effect from a reflection signal and repeatedly generates a blood flow image representing a spatial distribution associated with power of the blood flow signal at the frame rate. A power average value associated with a frame or local region is calculated for the blood flow image. The blood flow image is corrected. In the correcting, a gain on the power values in the frame or local region in which the power average value exceeds the threshold are substantially reduced, and power values in the frame or local region in which the power average value is not more than the threshold are maintained.
