An electrohydraulic shock wave-generating system for extracorporeal therapy of renal stones or musculoskeletal disorders includes a shock wave generator, a micro high-sensitivity camera, and a gap-controlling unit. The shock wave generator includes a truncated ellipsoidal bowl and two electrodes, each electrode having a portion inside the bowl, with a gap being defined between the electrodes. The micro high-sensitivity camera acquires an image of the electrodes for finding a size of the gap. The gap-controlling unit controls the size of the gap and moves at least one of the electrodes to adjust the size of the gap. A medical treatment for fragmenting stones or for curing musculoskeletal disorders can be carried out without increasing the operational voltage applied to the electrodes under gap control provided by the system. The system also includes a computer control unit to provide automatic control of the gap.