An LED lamp comprises a lamp housing, a heat sink made of metal and mounted at a bottom side of the lamp housing, a plurality of LED modules, and a vapor chamber having a bottom surface thereof attached to a top surface of the heat sink and having a top surface thereof to which the LED modules are attached, a working liquid is sealed in the vapor chamber. The vapor chamber defines a sealed chamber therein, and the working liquid is phase changeable liquid and is sealed in the sealed chamber. A plurality of ribs is arranged in the vapor chamber for strengthening an integrity of the vapor chamber, and the ribs divide the sealed chamber into a plurality of communicating spaces.