PURPOSE: To convert the data from an ultrasonic reflected wave to image data at a high speed, by providing a weighting circuit for performing predetermined weighting to the digital data read from a memory means and an image data forming means for successively converting the weighted data to the image data.

CONSTITUTION: A data output means 1 outputs the digital data obtained from an ultrasonic reflected wave. The digital data obtained from the ultrasonic reflected wave is written in a memory means 2 composed of the addresses of a 2×n system and constituted of (n2) memory banks. Therefore, digital data necessary for performing predetermined weighting can be simultaneously read on the basis of the addresses of the 2×n system and the digital data subjected to predetermined weighting by weighting circuits 31W3m (m=n2) are obtained at a high speed and successively receive processing such as addition by an image data forming means 4 to be converted to image data for display and said image data is displayed on a display means 5.