To provide a self-repairing mat and a water leakage detection system, the detection precision of which can be enhanced and in which dirty water or the like can be prevented from being diffused through a damaged portion until the detected damaged portion is repaired.

The water leakage detection system 10 electrically detects whether or not liner sheets 8, 9, which are laid on the inside surface 17 of a sunken place 16 formed on the ground 19, are damaged. The self-repairing mat 1 is placed between the liner sheets 8, 9, measuring electrodes 11 are placed on the upper side of the self-repairing mat 1, current electrodes 12, 13 are placed respectively on the inside of the ground 19 and on the inside of the sunken place 16, and the measuring electrodes 11 and the current electrodes 12, 13 are connected to a constant current device 14. The self-repairing mat 1 has a sheet-like shape comprising: an inner layer 2 comprising a swellable material; and outer layers 3, 4 comprising materials, which are layered above and below the inner layer 2 and have water permeability. Electrical conductivity is imparted in at least any one of the outer layers 3, 4 layered above and below the inner layer 2, and the measuring electrodes 11 are placed on the upper side of the outer layers 3 or 4 in which the electrical conductivity is imparted.