Crash prevention device (1) for machine tools (2), preventing the collision of a moving part (3, 4, 10, 19) of the machine tool (2), preferably the a tool (3) or the machining head (19), with other machine tool parts (6, 7) or with a workpiece (5) allocated in the working area (8) of the machine tool (2) during a movement of the moving part (3, 4, 10, 19). According to the invention, a high voltage is applied between the electrical isolated moving part (3, 4, 10, 19) and other machine tool parts (6, 7) or with the workpiece (5) allocated in the working area (8). The inventive crash prevention device (1) includes an discharge detection means (15) which can detect electrical discharges (16) occurring between the monitored moving part (3, 4, 10, 19) and the workpiece (5) or other electrical conductive machine elements (6, 7) and signalize to the machine controller (17) of the machine tool (2) to stop or adapt the further movement of the moving part (3, 4, 10, 19). An imminent crash of the moving part (3, 4, 10, 19) with another part allocated in the working area (8) of the machine tool (2) is therewith prevented.