Abstract: A shock wave generator for use in an extracorporeal lithotripsy apparatus has a liquid-filled housing with an exit aperture for shock waves which are electromagnetically generated and conducted to a focusing element for focusing onto the calculi, and a plate-shaped element having a smaller cross-sectional area than the emitted shock wave is disposed in the path propagation of the shock wave. The plate-shaped element consists of a material having an acoustic impedance substantially corresponding to the acoustic impedance of the liquid in the housing, and having a propagation speed of sound therein which deviates from the propagation speed of sound in the liquid.