A battery pack case comprising: a battery pack lower case having an insertion-coupling ridge defined in a predetermined area on a bottom surface; and a battery pack upper case comprising a hook part with a bent portion in which an end portion protrudes at a position corresponding to the insertion-coupling ridge of the battery pack lower case, wherein the insertion-coupling ridge of the lower case and the hook part of the upper case are coupled to each other to establish a hook coupling structure, and wherein the battery pack lower case comprises: a through-hole formed by punching a predetermined area on the bottom surface of the battery pack lower case so that a predetermined area of the bent portion of the battery pack upper case is disposed to the inside; and a locking projection positioned, while spaced a predetermined height from the through-hole, in a predetermined area that is on a side surface of the battery pack lower case and corresponds to the hook part of the battery pack upper case, wherein the bent portion of the battery pack upper case is locked in the locking projection. wherein the battery pack lower case further comprises: a side wall part positioned on one side of the through-hole; and a bottom part positioned on the other side of the through-hole, wherein the bottom part supports a predetermined area on a non-protruding side of the bent portion of the hook part; and wherein the insertion-coupling ridge is a space which is defined between the locking projection and the through-hole and in which the bent portion of the hook part is positioned. a battery pack lower case having an insertion-coupling ridge defined in a predetermined area on a bottom surface; and a battery pack upper case comprising a hook part with a bent portion in which an end portion protrudes at a position corresponding to the insertion-coupling ridge of the battery pack lower case, wherein the insertion-coupling ridge of the lower case and the hook part of the upper case are coupled to each other to establish a hook coupling structure, and wherein the battery pack lower case comprises: a through-hole formed by punching a predetermined area on the bottom surface of the battery pack lower case so that a predetermined area of the bent portion of the battery pack upper case is disposed to the inside; and a locking projection positioned, while spaced a predetermined height from the through-hole, in a predetermined area that is on a side surface of the battery pack lower case and corresponds to the hook part of the battery pack upper case, wherein the bent portion of the battery pack upper case is locked in the locking projection. wherein the battery pack lower case further comprises: a side wall part positioned on one side of the through-hole; and a bottom part positioned on the other side of the through-hole, wherein the bottom part supports a predetermined area on a non-protruding side of the bent portion of the hook part; and a through-hole formed by punching a predetermined area on the bottom surface of the battery pack lower case so that a predetermined area of the bent portion of the battery pack upper case is disposed to the inside; and a locking projection positioned, while spaced a predetermined height from the through-hole, in a predetermined area that is on a side surface of the battery pack lower case and corresponds to the hook part of the battery pack upper case, wherein the bent portion of the battery pack upper case is locked in the locking projection. wherein the battery pack lower case further comprises: a side wall part positioned on one side of the through-hole; and a bottom part positioned on the other side of the through-hole, wherein the bottom part supports a predetermined area on a non-protruding side of the bent portion of the hook part; and a side wall part positioned on one side of the through-hole; and a bottom part positioned on the other side of the through-hole, wherein the bottom part supports a predetermined area on a non-protruding side of the bent portion of the hook part; and