A liquid presence detecting device which has a simple and compact configuration, and which is high in efficiency, and an air improving device having the detecting device are provided.The liquid presence detecting device incudes a magnesium-air battery 20, and an electrical load 40. When liquid exists in a detection point, the magnesium-air battery operates (generates electricity), and, when liquid does not exist in the detection point, the operation of the magnesium-air battery stops. Therefore, the liquid presence detecting device detects the presence of liquid, and functions also as a power supply. The air improving device includes the liquid presence detecting device functioning also as a power supply, a device body 1, and an air improver 10 which is detachably attached into the device body.
