A secondary battery pack , comprising: a plurality of cylindrical battery cells having electrode terminals formed at both ends thereof; a pack case having an accommodation portion formed to accommodate the plurality of cylindrical battery cells therein and at least one exposing portion perforated from an inside to an outside thereof; at least one heat dissipation plate configured in the form of a metal plate and located at the exposing portion of the pack case so that at least a portion thereof is exposed out through the exposing portion of the pack case ; and a heat transfer pad having a thermally conductive material in a solid state and interposed between the plurality of cylindrical battery cells and the heat dissipation plate , wherein the heat transfer pad includes an upper pad formed to surround an upper portion of the plurality of cylindrical battery cells and a lower pad formed to surround a lower portion of the plurality of cylindrical battery cells , wherein the upper pad and the lower pad respectively have a curved portion having a protruding structure (P1) protruding in an inner direction of the secondary battery pack to be interposed between the plurality of cylindrical battery cells and a recess structure (U1) dented in an outer direction of the secondary battery pack , and wherein a convex portion formed at a location corresponding to the protruding structure (P1) of the curved portion and ridged in the inner direction of the secondary battery pack is formed at an inner surface of the heat dissipation plate , and wherein an insert portion dented in the inner direction of the secondary battery pack is formed at an outer surface of the heat transfer pad facing the heat dissipation plate so that the convex portion is inserted therein. a plurality of cylindrical battery cells having electrode terminals formed at both ends thereof; a pack case having an accommodation portion formed to accommodate the plurality of cylindrical battery cells therein and at least one exposing portion perforated from an inside to an outside thereof; at least one heat dissipation plate configured in the form of a metal plate and located at the exposing portion of the pack case so that at least a portion thereof is exposed out through the exposing portion of the pack case ; and a heat transfer pad having a thermally conductive material in a solid state and interposed between the plurality of cylindrical battery cells and the heat dissipation plate , wherein the heat transfer pad includes an upper pad formed to surround an upper portion of the plurality of cylindrical battery cells and a lower pad formed to surround a lower portion of the plurality of cylindrical battery cells , wherein the upper pad and the lower pad respectively have a curved portion having a protruding structure (P1) protruding in an inner direction of the secondary battery pack to be interposed between the plurality of cylindrical battery cells and a recess structure (U1) dented in an outer direction of the secondary battery pack , and wherein a convex portion formed at a location corresponding to the protruding structure (P1) of the curved portion and ridged in the inner direction of the secondary battery pack is formed at an inner surface of the heat dissipation plate , and wherein an insert portion dented in the inner direction of the secondary battery pack is formed at an outer surface of the heat transfer pad facing the heat dissipation plate so that the convex portion is inserted therein. <EOS>