In a lead-acid storage battery including a container housing elements formed by alternately layering positive electrode plates and negative electrode plates with deformable separators interposed therebetween, the container includes a narrow portion having a small inside dimension in a width direction intersecting a layered direction of the elements, widths of the respective plates are smaller than the inside dimension in the width direction of the narrow portion of the container, and widths of the separators are greater than or equal to the inside dimension of the narrow portion of the container.