Provided is a cooling structure for a street lamp using light emitting diodes. The cooling structure comprises a heat-dissipating case having an installation portion therein, a printed circuit board installed within the installation portion, one or more light emitting diodes installed under the printed circuit board, a heat transfer unit for transferring heat to be generated from the light emitting diodes to the top of the heat-dissipating case and dissipating the heat to the outside, and reflection plates disposed at the bottom of the heat-dissipating case. The cooling structure is efficiently improved to quickly and rapidly dissipate heat generated from the light emitting diodes during turn-on. With this configuration of the cooling structure, the street lamp is protected from failure and has greatly improved durability. In addition, the light emitting structure is improved to inhibit loss of luminance. Therefore, the energy efficiency of the street lamp can be effectively improved.