High-pressure jets are being pursued in diesel engines in order to facilitate development of next-generation fuel injection systems aiming at high performance, high fuel economy, and low emissions of smoke. Cavitation erosion accompanying the use of high-pressure jets for diesel fuel injection pumps is a factor responsible for reduced equipment durability and performance. In response, the project reported here involved the production of test equipment for the purpose of replicating the behavior of a fuel injection pump as it would occur in an actual diesel engine, with erosion testing, and analysis of the shock pressure by the cavitation, and its generating part. As a result, the following behaviors were noted. (1) In the 3-dimensional analysis of an unsteady cavitation jet stream, the shock pressure by the cavitation and its generating part can be predicted. (2) If the exit clearance of a hole is adjusted, the generating position of a erosion is controllable.