PURPOSE: To enhance the reliability of the connection between cells, which is performed by connecting the electrode poles of the cells through a penetrating hole provided on the partition wall of a container, by making the former electrode poles to have a given shape, and by pressing and fusing smooth annular parts by preliminary current feeding, before the electrode poles are subjected to resistance welding.

CONSTITUTION: A partition wall 4 in a container is provided with a penetrating hole, through which electrode poles 9 and 9' are connected by resistance welding. Each of the poles 9 and 9' is provided with a disclike projection 10 which can be closely fitted in the penetrating hole. The projection 10 consists of a circular irregular part 11 having fine irregularity and a smooth annular part 12 which surrounds the part 11. The back of the projection 10 is provided with a concave part 13 in which an electrode is fitted during the pressure current feeding. In connecting the electrode poles 9 and 9', the smooth annular parts 12 are subjected to pressure fusion by preliminary current feeding carried out with an electrode 14. After that, the pressure current feeding is carried out by use of an electrode, which touches the concave part 13 and presses and holds the back of the ring 12 in an insulating manner, thus the poles 9 and 9' undergo resistance welding and cells are connected.