Microbubbles are expected as carriers of acoustic targeted drug/gene delivery therapy. Because microbubbles diffuse in human body after injection, we have proposed a technique that controls catheter which can deliver microbubbles directly to the target position in blood vessels using ultrasound emitted from the body surface. To apply this technique in vivo, robotic positioning of therapeutic devices on body surface is required. For this purpose, we have developed a robotic system using parallel link robot, which has both diagnostic/therapeutic devices. In this paper, first we describe the algorithm of ultrasonic catheter control system. Then, we performed the accuracy evaluation of focal point using robotic positioning. The accuracy was about 1.5 mm, which is less than the beam width of sound pressure distribution. Finally, we demonstrated the ultrasonic catheter control experiment at the bifurcation of in vitro blood vessel and the catheter was controlled to the target path in 100% induction rate.