PURPOSE: To reject hard pictur toward lateral direction and to achieve sharp picture, by delaying a readout data from a video storage device for one scanning line's share, obtaining the average value of the next line data, performing D/A conversion and making TV display even for the intermediate value of tone difference of input data.

CONSTITUTION: A video data being reflected echo from a receiver constituting an ultrasonic wave diagnostic device is applied to an A/D cnverter 11, and the converted video data is written in a video storage device 12. The video data not converted is written in the storage device 12 by using a write-in/readout control circuit 13, and the readout is made by the standard TV scanning. The address designation for the storage device 12 is made by an address control circuit 14. The picture data of the storage device 12 is read out at the standard TV scanning and stored in a line data storage device 15 by one scanning line's share and also transmitted to an operation circuit 16, where the data is processed in every picture element on the basis of the equation from the picture data of the storage devices 12, 15 and is displayed on a monitor TV via a D/A converter 17.