A battery pack comprising: a plurality of battery cells, each comprising a terminal surface on which a terminal unit is arranged, a bottom surface opposite the terminal surface, and first and second side surfaces connecting the terminal surface to the bottom surface; a pack case, P1, P2, accommodating the plurality of battery cells in two rows such that the bottom surfaces face each other, and comprising: a flow path plate between the bottom surfaces of the battery cells in the two rows, and comprising channels buried in the flow path plate defining a plurality of flow paths accommodating a flow of a cooling medium, and first and second tanks, T1, T2 extending across the first and second side surfaces of the battery cells and fluidly connected to the plurality of flow paths, the tanks comprising first and second base plates (101, 102) and first and second cover plates covering the respective first and second base plates to form spaces between the cover plates and the base plates that are arranged to receive the cooling medium, wherein the first cover plate comprises an opening as a tank inlet through which the cooling medium is configured to be supplied to the first tank, the second cover plate comprises an opening as a tank outlet through which the cooling medium is configured to be discharged from the second tank, and the first and second base plates include openings corresponding to the flow paths. a plurality of battery cells, each comprising a terminal surface on which a terminal unit is arranged, a bottom surface opposite the terminal surface, and first and second side surfaces connecting the terminal surface to the bottom surface; a pack case, P1, P2, accommodating the plurality of battery cells in two rows such that the bottom surfaces face each other, and comprising: a flow path plate between the bottom surfaces of the battery cells in the two rows, and comprising channels buried in the flow path plate defining a plurality of flow paths accommodating a flow of a cooling medium, and first and second tanks, T1, T2 extending across the first and second side surfaces of the battery cells and fluidly connected to the plurality of flow paths, the tanks comprising first and second base plates (101, 102) and first and second cover plates covering the respective first and second base plates to form spaces between the cover plates and the base plates that are arranged to receive the cooling medium, wherein the first cover plate comprises an opening as a tank inlet through which the cooling medium is configured to be supplied to the first tank, the second cover plate comprises an opening as a tank outlet through which the cooling medium is configured to be discharged from the second tank, and the first and second base plates include openings corresponding to the flow paths. a flow path plate between the bottom surfaces of the battery cells in the two rows, and comprising channels buried in the flow path plate defining a plurality of flow paths accommodating a flow of a cooling medium, and first and second tanks, T1, T2 extending across the first and second side surfaces of the battery cells and fluidly connected to the plurality of flow paths, the tanks comprising first and second base plates (101, 102) and first and second cover plates covering the respective first and second base plates to form spaces between the cover plates and the base plates that are arranged to receive the cooling medium, wherein the first cover plate comprises an opening as a tank inlet through which the cooling medium is configured to be supplied to the first tank, the second cover plate comprises an opening as a tank outlet through which the cooling medium is configured to be discharged from the second tank, and the first and second base plates include openings corresponding to the flow paths.