A light-emitting diode (LED) lamp includes a columnar body having a plurality of heat-radiating fins, an LED supporting end, and a mounting end; a first conducting plate disposed on the LED supporting end; an LED having a first electrode in electric contact with the first conducting plate; a second conducting plate in electric contact with a second electrode of the LED; a cap having a rear coupling end covered around the LED supporting end of the columnar body and a front end defining a central opening to enclose a light-emitting section of the LED therein; a first annular gasket disposed between the rear coupling end of the cap and the LED supporting end of the columnar body; and a second annular gasket disposed between the light-emitting section and the central opening of the cap. Therefore, the LED lamp is waterproof and easy to maintain, and allows good heat radiation.