A protective case for smart watch may include a main body disposed around a smart watch to provide the elastic protection effect. The main body formed in a frame shape has two connecting edges, a controlling edge, and an audio edge, which are formed with the same thickness. The two connecting edges are formed in parallel, and each of the connecting edges has an engaging slot to couple with the watch strap of the smart watch. An audio recess concavely formed on an inner surface of the audio edge is configured to couple with a lateral side of the smart watch. The audio recess has a bottom portion communicated with the location of the speaker of the smart watch, and the audio recess is extended to the display of the smart watch to form a top opening.