A lead-acid battery comprising: an electrode plate group; and an electrolyte containing sulfuric acid, wherein the electrode plate group includes: a plurality of positive electrodes; a positive electrode strap that connects the plurality of positive electrodes in parallel; a plurality of negative electrodes; a negative electrode strap that connects the plurality of negative electrodes in parallel; and separators interposed between the positive electrodes and the negative electrodes that are adjacent to each other, each of the plurality of positive electrodes includes: a positive electrode active material; a positive electrode grid that supports the positive electrode active material thereon; and a positive electrode lug portion that is integral with the positive electrode grid and connects the positive electrode to the positive electrode strap, each of the plurality of negative electrodes includes: a negative electrode active material; a negative electrode grid that supports the negative electrode active material thereon; and a negative electrode lug portion that is integral with the negative electrode grid and connects the negative electrode to the negative electrode strap, the positive electrode grid contains antimony, a side surface of the negative electrode lug portion includes a surface layer portion containing bismuth, the negative electrode lug portion is welded to a principal surface of the negative electrode strap, and a fillet containing bismuth is formed at a boundary between the principal surface of the negative electrode strap and the side surface of the negative electrode lug portion, and the bismuth content in the fillet is 10 mass% or more. an electrode plate group; and an electrolyte containing sulfuric acid, wherein the electrode plate group includes: a plurality of positive electrodes; a positive electrode strap that connects the plurality of positive electrodes in parallel; a plurality of negative electrodes; a negative electrode strap that connects the plurality of negative electrodes in parallel; and separators interposed between the positive electrodes and the negative electrodes that are adjacent to each other, each of the plurality of positive electrodes includes: a positive electrode active material; a positive electrode grid that supports the positive electrode active material thereon; and a positive electrode lug portion that is integral with the positive electrode grid and connects the positive electrode to the positive electrode strap, each of the plurality of negative electrodes includes: a negative electrode active material; a negative electrode grid that supports the negative electrode active material thereon; and a negative electrode lug portion that is integral with the negative electrode grid and connects the negative electrode to the negative electrode strap, the positive electrode grid contains antimony, a side surface of the negative electrode lug portion includes a surface layer portion containing bismuth, the negative electrode lug portion is welded to a principal surface of the negative electrode strap, and a fillet containing bismuth is formed at a boundary between the principal surface of the negative electrode strap and the side surface of the negative electrode lug portion, and the bismuth content in the fillet is 10 mass% or more.