There is provided a first storage for storing digital reception beam data converted from a reception beam formed from an ultrasonic received signal a first control component for controlling reading and writing of data from/in the first storage a filter coefficient calculation portion for calculating a filter coefficient based on information on the reception beam, the information including a positional relationship between the reception beam and a transmission beam and a first spatial filter operation portion for subjecting each of a plurality of the reception beam data including data of beams received in parallel from a single transmission beam to filtering processing for reducing a difference in image quality between adjacent beams based on the filter coefficient. Image data output from the first spatial filter operation portion are converted into scanning of a display monitor so as to display an image on the display monitor.
