A switching device includes a first enclosure containing a switch, a rod-shaped second enclosure having a second end connected to the first enclosure, a detector unit in the second enclosure, and a float disposed around the second enclosure and capable of moving along it. As the float moves from the first end of the second enclosure toward the second end, when the float enters a first position range, a first position sensor senses the float and transmits a first sensing signal to a detection circuit; when the float enters a second position range, a second position sensor senses the float and transmits a second sensing signal to the detection circuit. The detection circuit close a switch in response to the second sensing signal to turn on an external appliance. The switching device is flexible, reliable, and inexpensive to produce.