The present disclosure relates to an MIMO antenna apparatus, and in particular, includes a PCB having at least one heat-generation element provided on one surface thereof, a first heat-dissipation part disposed to cover one surface of the PCB, having a through hole formed in a portion corresponding to the position provided with the heat-generation element, and having a plurality of vertical heat-dissipation fins formed to be extended in a direction perpendicular to the outside surface thereof, and a second heat-dissipation part detachably coupled to the through hole to contact one surface of the heat-generation element to receive heat from the heat-generation element and to dissipate heat at a long distance father than the first heat-dissipation part, thereby enhancing heat-dissipation performance and expanding universality of a product.