Method and apparatus for manufacturing battery module and unit battery cell for use in battery module

In the method for manufacturing the battery module according to this invention, after a pair of welding upper/lower electrodes 21, 22 or 23, 24 are arranged in contact on the cases 16, 16 of adjacent unit cells 10a, 10b of a plurality of unit cells aligned in a line, a welding current is passed between the pair of welding upper electrodes 21, 23 from a welding power source while both ends of the unit cells 10a, 10b 10c are pressurized by pressurizing members 31, 32 under a prescribed pressure. Thus, Joule heat is generated at the contact portion between the bottom of the outer case 16 of the unit cell 10a and the positive polarity terminal 18 of the unit cell 10b so that the contact portion melts. Accordingly, the bottom of the outer case 16 of the unit cell 10a and the positive polarity terminal 18 of the unit cell 10b are welded to each other at the contact portion.