A heat-dissipating structure for the expansion board architecture is provided. A fixing element disposed on the heat-absorbing substrate fixes the motherboard and the first expansion board. The heat-generating elements on the motherboard or the first expansion board are directly in touch with the heat-absorbing surface of the heat-absorbing substrate to absorb their heat. The heat-dissipating board extended from the side of the heat-absorbing substrate then dissipates the heat absorbed by the heat-absorbing substrate. The structure thus solves the problems that existing heat-dissipating structures occupy larger space and therefore cannot be effectively used in an expansion board architecture to dissipate heat produced by the heat-generating elements between the motherboard and the expansion board and that it is likely to have assembly tolerance. Using the structure can reduce the space and the assembly tolerance, but effectively enhance heat dissipation in the expansion board architecture.