A battery pack, comprising: at least one battery connecting unit; a lower housing including the at least one battery connecting unit, wherein the lower housing includes at least one support, wherein the at least one battery connecting unit is located at one of the at least one support of the lower housing and inserted into a fitting hole of the one respective support; a battery laminate accommodated in the lower housing and electrically connected to the at least one battery connecting unit; an upper housing made of plastic and configured to cover the lower housing and the battery laminate, wherein: the at least one battery connecting unit includes a metal terminal and a plastic member, wherein the plastic member is configured to come into contact with the upper housing and the metal terminal inserted into the upper housing, wherein the metal terminal is provided through the upper housing, and the plastic member is fixed to the upper housing by welding at a lower portion of the upper housing, wherein the plastic member surrounds a lower portion of the metal terminal in a cylindrical shape and exposes an upper portion of the metal terminal, wherein the plastic member includes a lower buffer and an upper buffer which are positioned in order and formed integrally, and wherein both the lower buffer and upper buffer have a cylindrical shape, wherein the lower buffer has a smaller outer diameter than the upper buffer, and wherein the metal terminal is made of a circular pillar and includes an annular protrusion and a gear-shaped protrusion pattern, formed at a sidewall of the circular pillar, in the lower portion of the metal terminal, wherein the lower buffer surrounds the annular protrusion, and the upper buffer surrounds the gear-shaped protrusion pattern. at least one battery connecting unit; a lower housing including the at least one battery connecting unit, wherein the lower housing includes at least one support, wherein the at least one battery connecting unit is located at one of the at least one support of the lower housing and inserted into a fitting hole of the one respective support; a battery laminate accommodated in the lower housing and electrically connected to the at least one battery connecting unit; an upper housing made of plastic and configured to cover the lower housing and the battery laminate, wherein: the at least one battery connecting unit includes a metal terminal and a plastic member, wherein the plastic member is configured to come into contact with the upper housing and the metal terminal inserted into the upper housing, wherein the metal terminal is provided through the upper housing, and the plastic member is fixed to the upper housing by welding at a lower portion of the upper housing, wherein the plastic member surrounds a lower portion of the metal terminal in a cylindrical shape and exposes an upper portion of the metal terminal, wherein the plastic member includes a lower buffer and an upper buffer which are positioned in order and formed integrally, and wherein both the lower buffer and upper buffer have a cylindrical shape, wherein the lower buffer has a smaller outer diameter than the upper buffer, and wherein the metal terminal is made of a circular pillar and includes an annular protrusion and a gear-shaped protrusion pattern, formed at a sidewall of the circular pillar, in the lower portion of the metal terminal, wherein the lower buffer surrounds the annular protrusion, and the upper buffer surrounds the gear-shaped protrusion pattern. the at least one battery connecting unit includes a metal terminal and a plastic member, wherein the plastic member is configured to come into contact with the upper housing and the metal terminal inserted into the upper housing, wherein the metal terminal is provided through the upper housing, and the plastic member is fixed to the upper housing by welding at a lower portion of the upper housing, wherein the plastic member surrounds a lower portion of the metal terminal in a cylindrical shape and exposes an upper portion of the metal terminal, wherein the plastic member includes a lower buffer and an upper buffer which are positioned in order and formed integrally, and wherein both the lower buffer and upper buffer have a cylindrical shape, wherein the lower buffer has a smaller outer diameter than the upper buffer, and wherein the metal terminal is made of a circular pillar and includes an annular protrusion and a gear-shaped protrusion pattern, formed at a sidewall of the circular pillar, in the lower portion of the metal terminal, wherein the lower buffer surrounds the annular protrusion, and the upper buffer surrounds the gear-shaped protrusion pattern.