A detection device for detecting a fishing device entering water and a method thereof are provided. The detection device includes a waterproof housing, a circuit board, a capacitive sensing module, and a control unit. The capacitive sensing module and the control unit are disposed on the circuit board. The capacitive sensing module is disposed adjacent to an inside wall surface of the waterproof housing and senses a capacitance value. The control unit receives the capacitance value and when the control unit makes a determination, according to the capacitance value, that the fishing device has entered water, the control unit generates a control signal to activate a to-be-controlled device.
