PURPOSE: To provide an ultrasonic diagnostic system which can display the state or acoustic scanning even when the acoustic frame rate is lowered.

CONSTITUTION: This ultrasonic diagnostic system provides an operational circuit l generating a digital signal of an ultrasonic scan type, a sound line memory 2 storing sound line data of a plurality of banks, a signal treating circuit 4 converting a sound line data read out of the sound line memory 2 to a signal of TV format and a cinememory 3 storing data for a plurality of images. Then, the bank of the sound line memory 2 performing reading out is switched by a TV frame period and the bank of the sound line memory 2 performing reading out is switched by an arbitrary period not so as to collide the period of reading out and control means 6 and 7 wherein the output data of the operational circuit 1, the same acoustic frame data stored in the cinememory 3 and a data of one preceeding acoustic frame stored in the cinememory 3 are synthsized and writing of data for one bank of the sound line memory 1 are provided.