Disclosed is a secondary battery pack including a plurality of cylindrical battery cells with improved cooling efficiency. The secondary battery pack includes 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.