Disclosed herein is a heat dissipation device for a power conversion module. The device includes a casing, a high-heat-dissipation heat sink and a circuit board. The casing includes a heat-dissipation fin unit which has heat dissipation fins arranged at positions spaced apart from each other by predetermined intervals. The casing has a mounting space therein. The high-heat-dissipation heat sink is installed in the mounting space of the casing. The circuit board is coupled to a lower surface of the casing. Therefore, the weight and size of the heat dissipation device can be reduced. In addition, the heat sink and the casing having the heat dissipation fins dissipate heat at the same time, thus enhancing the heat dissipation efficiency. Moreover, in an optimal design, the high-heat-dissipation heat sink is located at a position corresponding to a part which generates high heat so that the heat dissipation efficiency can be maximized.