Provided herein is a lead-acid battery for which the risk of breakage of a current collecting lug part of a plate while in use is eliminated by simple means. At least a positive plate group of the lead-acid battery includes: one or more plates each including a current collector having a current collecting portion formed by expanding or punching a lead alloy sheet manufactured by cold rolling, and one or more current collecting lug parts unitarily formed with the current collecting portion; and a strap formed by a cast-on strap casting method and coupled to the one or more current collecting lug parts. The current collecting lug part is formed with an elongated protrusion extending in a direction away from the current collecting portion. The elongated protrusion continuously extends in a direction toward the current collecting portion of the plate from inside the strap.