A battery pack that is loaded in an electric vehicle in a removable manner and supplies power to the electric vehicle comprising: a plurality of batteries that can be charged; a case that houses the batteries; and a connector (3; 43) that connects to the electric vehicle connecting terminals to supply power from the batteries housed in the case; wherein the battery pack is inserted downward into, and disposed in a fixed position in a loading cavity in the electric vehicle to connect the connector (3; 43) to the connecting terminals mounted in the electric vehicle and supply power to the electric vehicle, wherein the connector (3; 43) is attached to the case in an orientation that establishes an insertion section on the underside of the case, and this enables the connector (3; 43) to connect to the connecting terminals mounted in the electric vehicle via the weight of the battery pack, wherein the case is provided with a case extension that protrudes from the surface of the case and holds the connector (3; 43) inside, wherein the bottom surface of the case extension is disposed above the bottom surface of the case, and the bottom surface of the case extension has a connector window opened to expose the connector (3; 43) insertion section outside the case, wherein the case extension is inserted in the electric vehicle loading cavity to connect the connector (3; 43) to the connecting terminals mounted in the electric vehicle, characterized in that the connector is provided with a connector case housing flexible contacts that make electrical connection with the connecting terminals; insertion sections are opened through the bottom surface of the connector case for connecting terminal insertion, and wherein the connector case is attached to the battery pack case in a manner that allows it to move freely in the direction of connecting terminal insertion. a plurality of batteries that can be charged; a case that houses the batteries; and a connector (3; 43) that connects to the electric vehicle connecting terminals to supply power from the batteries housed in the case; wherein the battery pack is inserted downward into, and disposed in a fixed position in a loading cavity in the electric vehicle to connect the connector (3; 43) to the connecting terminals mounted in the electric vehicle and supply power to the electric vehicle, wherein the connector (3; 43) is attached to the case in an orientation that establishes an insertion section on the underside of the case, and this enables the connector (3; 43) to connect to the connecting terminals mounted in the electric vehicle via the weight of the battery pack, wherein the case is provided with a case extension that protrudes from the surface of the case and holds the connector (3; 43) inside, wherein the bottom surface of the case extension is disposed above the bottom surface of the case, and the bottom surface of the case extension has a connector window opened to expose the connector (3; 43) insertion section outside the case, wherein the case extension is inserted in the electric vehicle loading cavity to connect the connector (3; 43) to the connecting terminals mounted in the electric vehicle, characterized in that the connector is provided with a connector case housing flexible contacts that make electrical connection with the connecting terminals; insertion sections are opened through the bottom surface of the connector case for connecting terminal insertion, and wherein the connector case is attached to the battery pack case in a manner that allows it to move freely in the direction of connecting terminal insertion.