PURPOSE: To obtain a plate with improved discharge performance easily, at a low cost, by mixing a conductive agent into a powdery active material before the mixture is pressed and molded, and sintering the surfaces of a metal fiber or the like instantaneously by high-frequency dielectric heating.

CONSTITUTION: A powdery active material such as nickel hydroxide or cadmium oxide is added with a metal powder or a metal fiber used as a conductive agent, and the mixture is pressed and molded. After that, the surfaces of the above metal powder or metal fiber are sintered instantaneously by high-frequency dielectric heating. By the means mentioned above, a plate with high discharge performance can be easily obtained at a low cost.