To achieve a higher effect for reducing speckles with a small deterioration in resolving power and also separate the speckles so far harder to separate merely by amplitudes and shapes from other signals.

An apparatus has an ultrasonic wave probe in which a plurality of elements is so arrayed as to transmit ultrasonic waves to a subject while outputting received signals by receiving ultrasonic wave signals reflected from the subject and a speckle reduction means which reduces the speckles utilizing a difference in characteristics of changes between the speckles and other signals in the amplitudes and phases of the ultrasonic wave signals obtained by variably altering assumed sound velocities preset for the actual sound velocities of the ultrasonic waves transmitted to the subject. Also provided is a signal separation means which separates the speckles from other signals on the basis of changes in distance phase of RF data.