The present invention, respectively in close contact with the inner wall of the borehole and the first packer and the second packer for forming a hollow enclosed between the intervals that are spaced apart from each other, and having a receiving space therein and through said first packer and the second packer connection is to be formed with the hollow part of ground water to be observed the water level of the ground water which is combined to be respectively in communication with the chamber having an inlet hole in communication with the hollow portion, and the chamber to flow into the housing space flows into the first inner diameter of the observation tube and the second observation including a tube, the first to observe the water level changes according to the characteristics of the hydrogeological observation tube is formed to be larger than the inner diameter of the second observation tube, wherein a first observation tube or provide repair test device characterized in that the underground formation such that the second observation is optionally introduced into a tube.