To provide a device and method which can form an especially high-quality trench wall.

The device for forming the trench wall in the soil is provided with a frame, at least one lower cutting/mixed wheel, and at least one additional upper cutting/mixed wheel. The lower cutting/mixed wheel is arranged at the bottom of the frame, and the upper cutting/mixed wheel is arranged at the top of the frame. Then the frame is designed to have a smaller cross section than the cutting cross section of the at least one lower cutting/mixed wheel at the midpoint between the upper cutting/mixed wheel and the lower cutting/mixed wheel. The method of forming the trench wall in the soil by the device is also provided.