Thermal sensor and smoke and thermal fire detector

The problem to be solved by the present disclosure is to provide a thermal sensor that can reduce the opportunity of excessively reducing the heat of a gas flowing toward a thermal detection unit. A thermal sensor 1 includes a base 1b and a thermal sensor body 1a. The base 1b is to be mounted on a mounting surface X11 of a building. The thermal sensor body 1a has a bottomed cylindrical shape and is to be attached to the base 1b. The thermal sensor body 1a comprises an opening 7, a plate 2, a thermal detection unit 3, and at least one wall member 522. The at least one wall member 522 controls the flow of the gas to cause the gas through the opening 7 to flow toward the thermal detection unit 3. The at least one wall member 522 separates a flow of gas that has entered the thermal sensor body 1a from the external space SP2 through the opening 7 into a plurality of gas flows and directs one of the plurality of gas flows that has been separated to flow alongside the inner surface of the thermal sensor body 1a towa