PURPOSE: To make a porous negative active matter to be firmly linked to an expanded network, and reduce the ratio by weight of the expanded network to the active matter by forming a dense network by locally compressing the active matter so as to decrease the porosity of the active matter.

CONSTITUTION: After fine plastic belts 2, which are used for adjusting the thickness of a paste 3, are fixed to both side peripheries of a relatively rough expanded network 1 prepared from a thinly rolled lead-alloy plate, the paste 3 is packed into the network 1. Thus prepared electrode plate, after being cut into a proper size, is opposed to an anode in dilute sulfuric acid, and subjected to chemical conversion formation by leading the thin expanded grid. After the chemical conversion is completed, thus made negative plate (a) principally consisting of foamed lead is sufficiently washed with water so as to remove the remaining sulfuric acid, thereby obtaining a negative active matter 4. Next, the negative active matter 4 is locally compressed with a press die 6 so as to obtain a dense network 5. After such pressing work is performed on the large negative active matter 4 several times, the negative plate (a) is trimmed so as to obtain a negative plate.