An illuminative device, offers an optical device that is regulated by one hand and a LED circuit board that is sealed in waterproof and quick cooling structure. The illuminator, comprises a main body included a tube container for at least a battery and a narrow tube in the front end, a switch device set in rear end of the main body, which includes a battery cover, a screw thread portion for screwing to the main body, a switch board that sets a trigger on one end and a spring pole on the other end for a connection to the battery, and a elastic switch button that sets on the switch board, an emitting device included a LED circuit board and a tube base as a radiator, and a optical device included a sleeve with an inside circular stop flange at the rear end and an inside screw thread at the front end, a lens that holds at the front end of the sleeve, and a fastening ring with an outside screw thread for fixing the lens into the sleeve.In according assembly, the illuminative device can switch on/off the power by the switch device at the rear end, and regulates the optical device by one hand to project from a narrow to a wide light spot.