A battery pack manufacturing device includes a transferring part for transferring a plurality of unit cells, an adjusting part for adjusting a position of a pack frame in which the unit cells are accommodated, and a vertical pressing part that vertically presses the unit cells accommodated in the pack frame. The transferring part includes a seating part on which the unit cells are seated. The unit cells are vertically dropped and mounted in accommodating parts of the frame when an opening and closing part of each seating part is opened.