Disclosed herein is a battery cell bending device for bending outer edges of a battery cell configured to have a structure in which an electrode assembly including a positive electrode, a separator, and a negative electrode is mounted in a battery case, and the battery case is sealed by thermal bonding, the battery cell bending device including a base plate, on which the battery cell is loaded, a pair of bending guides inserted respectively between left and right outer edges of a battery case and an outer surface of an electrode assembly receiving part in a state in which the battery cell is loaded on the base plate, pressing rollers for pressing the outer edges of the battery case toward the bending guides to bend the outer edges of the battery case such that the outer edges of the battery case are adjacent to the outer surface of the electrode assembly receiving part, and heating members disposed adjacent to the pressing rollers for heating the bent outer edges of the battery case.