An LED illuminating device includes an optical section, an electrical section, and a heat dissipation section. The heat dissipation section is provided with a heat sink and at least one heat pipe therein. The heat sink includes a metal tube, a plurality of metal fins extending radially and outwardly from the metal tube, and a heat-absorbing plate attached to a bottom of the metal tube. A chamber is axially recessed from a top of the metal tube to the heat-absorbing plate. The heat pipe includes an evaporating section and a condensing section. The evaporating section of the heat pipe is attached to an inner surface of the heat-absorbing plate. The condensing section of the heat pipe is attached to an inner circumferential surface of the metal tube. The light source is attached to an outer surface of the heat-absorbing plate.