A wire detachment-preventing structure includes: a circuit board box, a housing provided with a wiring outlet and constituting the circuit board box, a terminal block for connecting a wire and provided on the circuit board box and provided with a wiring inlet; the circuit board box is provided with a wire detachment-preventing rib, the wiring inlet and the wiring outlet are provided on one same side of the wire detachment-preventing rib, a first passageway is formed between the wiring outlet and the wire detachment-preventing rib, a second passageway is formed between the wire detachment-preventing rib and the housing, and the wire from the wiring outlet bypasses the wire detachment-preventing rib through the second passageway and leads to the wiring inlet through the first passageway so as to form a U shape. By use of the wire detachment-preventing rib, the wire is not easily detached from the wiring inlet.