PURPOSE: To reduce the coming off of an active material and to increase conductivity by stacking metallic supporting plates having continuous, three-dimensional pores on both sides of a paste-filled plate, and pressing them to form one body.

CONSTITUTION: Active material paste is filled in a metal structural plate having continuous, three-dimensional pores, and dried to form a filled plate 1. Metallic supporting plates 2 having continuous, three-dimensional pores are stacked on both sides of the filled plate 1 to form sandwiched structure. The stacked plates are pressed in the direction of the thickness to make them in one body. The coming off of an active material from the filled plate 1 is prevented and conductivity is increased.