To install a underground continuous wall in the ground where an obstacle is contained with the obstacle remained in the ground.

The underground continuous wall cutter 10 is provided with a frame 13 having a linear excavation connection part 30 connected above and also including two pairs of excavation wheels 20, 20' below. The frame 13 has a tapered shape narrowing from the lower part where the excavation wheels 20, 20' are arranged toward the upper part connected with the excavation connection part 30. The tapered shape makes the excavation wheels fit in under the embedded obstacles, so that a prepared hole in the underground continuous wall can be formed.