A humidity sensor according to the present examples include a sensor portion for detecting humidity in the ambient environment, and a power supply portion for applying an AC voltage to the sensor portion, wherein the sensor portion is structured so as to have an impedance that is higher than a sensor portion of a conventional humidity sensor. As a result, it is possible to reduce the amount of power consumed in the sensor portion when compared to that of a conventional humidity sensor. Doing so makes it possible to reduce the amount of electrical power consumed in the humidity sensor as a whole in the present invention, including the sensor portion, when compared to that of a conventional humidity sensor.