A battery pack comprising: a battery module assembly configured to have a structure in which two or more battery modules, each of which comprises battery cells arranged in an upright state such that electrode terminals of the battery cells are directed upward, are arranged such that the battery modules are adjacent to each other, wherein each of the battery modules is configured to have a structure in which two or more unit modules, each of which comprises one or more battery cells mounted in a cartridge, are arranged such that the unit modules are adjacent to each other, wherein the cartridge is configured to have a frame structure to fix outer edge sealed portions of the battery cells located at opposite sides of the cartridge; and outward protrusions are formed at a lower end of one side or lower ends of opposite sides of the frame; and a base plate, on a top of which the battery module assembly is loaded; and a hold down bracket having one side region covering the outward protrusions of the frames and the other side region coupled to the base plate so as to correctly fix the respective battery modules of the battery module assembly to the base plate; characterized in that: depressions configured to be fixed to the hold down bracket are formed between adjacent outward protrusions of neighbouring cartridges; the hold down bracket is provided with fixing parts formed in a shape in which the fixing part is disposed in tight contact with the depressions and the hold down bracket is formed in a shape in which the hold down bracket is disposed in tight contact with the outside of the outward protrusion in a region at which the fixing part is not formed, and a height of the cartridge is greater than a lower end width of the cartridge in a state in which the cartridge is loaded on the base plate. a battery module assembly configured to have a structure in which two or more battery modules, each of which comprises battery cells arranged in an upright state such that electrode terminals of the battery cells are directed upward, are arranged such that the battery modules are adjacent to each other, wherein each of the battery modules is configured to have a structure in which two or more unit modules, each of which comprises one or more battery cells mounted in a cartridge, are arranged such that the unit modules are adjacent to each other, wherein the cartridge is configured to have a frame structure to fix outer edge sealed portions of the battery cells located at opposite sides of the cartridge; and outward protrusions are formed at a lower end of one side or lower ends of opposite sides of the frame; and a base plate, on a top of which the battery module assembly is loaded; and a hold down bracket having one side region covering the outward protrusions of the frames and the other side region coupled to the base plate so as to correctly fix the respective battery modules of the battery module assembly to the base plate; characterized in that: depressions configured to be fixed to the hold down bracket are formed between adjacent outward protrusions of neighbouring cartridges; the hold down bracket is provided with fixing parts formed in a shape in which the fixing part is disposed in tight contact with the depressions and the hold down bracket is formed in a shape in which the hold down bracket is disposed in tight contact with the outside of the outward protrusion in a region at which the fixing part is not formed, and a height of the cartridge is greater than a lower end width of the cartridge in a state in which the cartridge is loaded on the base plate. depressions configured to be fixed to the hold down bracket are formed between adjacent outward protrusions of neighbouring cartridges; the hold down bracket is provided with fixing parts formed in a shape in which the fixing part is disposed in tight contact with the depressions and the hold down bracket is formed in a shape in which the hold down bracket is disposed in tight contact with the outside of the outward protrusion in a region at which the fixing part is not formed, and a height of the cartridge is greater than a lower end width of the cartridge in a state in which the cartridge is loaded on the base plate.