The invention provides a light-emitting device, which includes a water-proof enclosure, a motion-actuated switch, a controller, a memory unit, a light-emitting array, a driving unit, and a battery. The motion-actuated switch is capable of generating a triggering signal if an external force presses on it. Furthermore, when the controller is under the start condition, it can selectively generate a lighting signal according to the triggering signal. The memory unit is applied for storing a plurality of default patterns. The light-emitting array includes a plurality of light-emitting diodes. The driving unit is capable of selecting one of the default patterns according to the lighting signal in a pre-determined way, and driving the light-emitting array lighting based on the default pattern. Particularly, the pre-determined way is in a proper sequence.