The invention discloses an underwater lighting device which comprises a light source, an overwater guiding light device and an underwater guiding light device, wherein the light source is positioned on the exterior of the water and above the water surface, and lights from the light source enter the water by virtue of the overwater guiding light device and the underwater guiding light device; the underwater guiding light device comprises a light guide body and an air layer structure, and the air layer structure is covered on the periphery of the light guide body; and the light guide body is isolated from the periphery water, and an air layer in the air layer structure can ensure that the lights in the guiding light body to generate a total reflection action.