A battery pack comprising: at least one battery module including a plurality of battery cells and a module case having an accommodating space to accommodate the plurality of battery cells therein; and a pack housing including an upper case that has an internal structure to cover a top portion of the at least one battery module and includes a cover portion having an external structure having a curved surface entirely from one end to the other end, the upper case comprises a first edge portion provided along a bottom end surface of the cover portion and protruding and extending in an outward direction, and a lower case that has an internal structure to surround a bottom portion of the at least one battery module and includes a mounting portion having an external structure having a curved surface entirely from one end to the other end, the lower case comprises a second edge portion provided along a top end surface of the mounting portion and protruding and extending in the outward direction, wherein the first edge portion and the second edge portion are combined to each other so that the upper case and the lower case are sealed and are configured to maintain the inside thereof in a negative pressure state, and wherein the upper case includes a fastening hole configured to be bolted, the module case includes a through hole into which a bolt is inserted, and the lower case includes a fastening groove at a location corresponding to the fastening hole in an up-and-down direction, and wherein the battery pack further comprises at least one long bolt configured to combine and fix the upper case, the at least one battery module, and the lower case to each other by insertion into a fastening hole (H1a) in the upper case, a corresponding through hole in the module case and a corresponding fastening groove (H2a) in the lower case. at least one battery module including a plurality of battery cells and a module case having an accommodating space to accommodate the plurality of battery cells therein; and a pack housing including an upper case that has an internal structure to cover a top portion of the at least one battery module and includes a cover portion having an external structure having a curved surface entirely from one end to the other end, the upper case comprises a first edge portion provided along a bottom end surface of the cover portion and protruding and extending in an outward direction, and a lower case that has an internal structure to surround a bottom portion of the at least one battery module and includes a mounting portion having an external structure having a curved surface entirely from one end to the other end, the lower case comprises a second edge portion provided along a top end surface of the mounting portion and protruding and extending in the outward direction, wherein the first edge portion and the second edge portion are combined to each other so that the upper case and the lower case are sealed and are configured to maintain the inside thereof in a negative pressure state, and wherein the upper case includes a fastening hole configured to be bolted, the module case includes a through hole into which a bolt is inserted, and the lower case includes a fastening groove at a location corresponding to the fastening hole in an up-and-down direction, and wherein the battery pack further comprises at least one long bolt configured to combine and fix the upper case, the at least one battery module, and the lower case to each other by insertion into a fastening hole (H1a) in the upper case, a corresponding through hole in the module case and a corresponding fastening groove (H2a) in the lower case.