An LED lamp includes a heat sink, an LED module attached to a top surface of the heat sink in a thermal conductive relationship therewith and a cover coupled to the top surface of the heat sink and covering the LED module. The heat sink is column-shaped and has a central axis. The heat sink comprises a conducting member and a plurality of spaced and parallel fins extending outwardly from the conducting member. A distance between each of inner edges of the fins and the central axis is gradually decreased from the top surface to a bottom surface of the heat sink.