Abstract: A leak sensor includes a base layer which is formed by soaking a plate-shaped structure into a resin solution, particularly a fluorine-based resin solution, or formed of a plate-shaped structure of a resin, particularly a fluorine-based resin; and a sensor layer in which a leak detection part having a predetermined area is formed by coating or printing a mixture of a liquid resin or a liquid fluorine-based resin and a conductive material on the base layer in a predetermined pattern, wherein the leak detection part of the sensor layer is formed on a side surface of the sensor layer to be exposed to the outside. Therefore, even though the sensor is not located just under the leaked fluid, the sensor becomes in contact with the fluid, and thus can detect the fluid leakage.