To provide a water leak generation position detection device and its method, capable of distinguishing and detecting the water leak position surely, even if plural water leak locations exist, and improving accuracy for detecting the water leak generation position.

This water leak generation position detection device is equipped with a sealing construction structure 1 for laying a sealing construction 2 of an electrical insulator, a surface electrode 12 installed on either of the front and the back of the sealing construction 2, plural point electrodes installed on the opposite side to the surface electrode 12, a first selection connection means for setting an applicator by selecting one from the plural point electrodes and connecting the electrode to the application side of a power source 4, a potential difference measuring means 5 for measuring the potential difference between the point electrodes except the applicator by a voltage applied between the applicator and the surface electrode 12, and a second selection connection means for setting potential difference measuring electrodes by selecting two point electrodes adjacent to the application electrode and connecting the electrodes to the potential difference measuring means 5. The device is used for detecting the water leak position of the sealing construction structure 1 from the measured potential difference and the position of the applicator. The device has a third selection connection means for connecting all point electrodes, except the selected applicator and the potential difference measuring electrodes, and the surface electrode 12 to the other terminal of the power source 4.