A leak detection sensor is disclosed for detecting a leaking liquid spilled from an adapter-coupling position, and includes a first conductive layer, an insulator and a second conductive layer. The first conductive layer includes a first through hole. The adapter-coupling position is located adjacent to the first through hole. The insulator includes a second through hole. The second conductive layer is connected to the first conductive layer through the insulator, and includes a conducting surface in fluid communication with the adapter-coupling position through the second through hole and the first through hole. The first conductive layer and the second conductive layer are insulated from each other through the insulator. When the leaking liquid is spilled into the first through hole and the second through hole, and contacts the conducting surface, the second conductive layer is conducted to the first conductive layer to form a conducting-resistance value.