Abstract: A diagnostic ultrasound apparatus includes an ultrasound probe for transmitting and receiving ultrasound waves to and from a patient to obtain echo data of the patient, an echo data memory in which the echo data are to be written by being identified with addresses S, B represented by a polar coordinate system, a frame memory in which the echo data read out from the echo data memory are to be written according to first addresses X, Y represented by a rectangular coordinate system, and an address generator for sequentially generating the first addresses X, Y which are used when the echo data are written into the frame memory. The apparatus further includes an address converting section for converting the addresses X, Y generated by the address generator into the polar coordinate addresses R, .theta..