A lead-acid battery comprising: a positive plate group; and a negative plate group, the positive plate group and the negative plate group each comprising: 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 (2,2') integrally formed with the current collecting portion; and a strap coupled to the one or more current collecting lug parts (2,2'), wherein: the one or more current collecting lug parts (2,2') included in the positive plate group are each formed with one or more elongated protrusions (3,3') extending continuously in a direction towards the current collecting portion, the one or more elongated protrusions (3,3') being formed to protrude on one surface of the current collecting lug part (2, 2') as a result of forming one or more elongated depressions in the other surface of the current collecting lug part (2,2') at a position corresponding to the one or more elongated protrusions (3,3'); characterized in that: the strap is formed by a cast-on strap-casting method; and the one or more elongated protrusions (3,3') each extend from inside the strap to outside the strap. a positive plate group; and a negative plate group, the positive plate group and the negative plate group each comprising: 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 (2,2') integrally formed with the current collecting portion; and a strap coupled to the one or more current collecting lug parts (2,2'), wherein: the one or more current collecting lug parts (2,2') included in the positive plate group are each formed with one or more elongated protrusions (3,3') extending continuously in a direction towards the current collecting portion, the one or more elongated protrusions (3,3') being formed to protrude on one surface of the current collecting lug part (2, 2') as a result of forming one or more elongated depressions in the other surface of the current collecting lug part (2,2') at a position corresponding to the one or more elongated protrusions (3,3'); characterized in that: the strap is formed by a cast-on strap-casting method; and the one or more elongated protrusions (3,3') each extend from inside the strap to outside the strap. 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 (2,2') integrally formed with the current collecting portion; and a strap coupled to the one or more current collecting lug parts (2,2'), wherein: the one or more current collecting lug parts (2,2') included in the positive plate group are each formed with one or more elongated protrusions (3,3') extending continuously in a direction towards the current collecting portion, the one or more elongated protrusions (3,3') being formed to protrude on one surface of the current collecting lug part (2, 2') as a result of forming one or more elongated depressions in the other surface of the current collecting lug part (2,2') at a position corresponding to the one or more elongated protrusions (3,3'); characterized in that: the strap is formed by a cast-on strap-casting method; and the one or more elongated protrusions (3,3') each extend from inside the strap to outside the strap. the one or more current collecting lug parts (2,2') included in the positive plate group are each formed with one or more elongated protrusions (3,3') extending continuously in a direction towards the current collecting portion, the one or more elongated protrusions (3,3') being formed to protrude on one surface of the current collecting lug part (2, 2') as a result of forming one or more elongated depressions in the other surface of the current collecting lug part (2,2') at a position corresponding to the one or more elongated protrusions (3,3'); characterized in that: the strap is formed by a cast-on strap-casting method; and the one or more elongated protrusions (3,3') each extend from inside the strap to outside the strap. the strap is formed by a cast-on strap-casting method; and the one or more elongated protrusions (3,3') each extend from inside the strap to outside the strap.