A flexible board includes a base layer, a wiring conductor layer that is located on the base layer, and a cover layer that is stacked over the base layer and covers the wiring conductor layer. A portion of the wiring conductor layer defines connecting portions that connect each of split electrodes of a flexible thermistor. The cover layer includes an opening that exposes the connecting portions, and receives the flexible thermistor. The split electrodes of the flexible thermistor are mounted on the connecting portions of the wiring layer. The height of the exposed surface of the flexible thermistor from the opening is substantially equal to the height of the surface of the cover layer.