The present invention provides a battery pack configured as follows: a plurality of battery cells (100) are laminated therein, such cells including a laminated-film housing material in which a positive terminal lead-out tab and a negative terminal lead-out tab are lead out in the same direction; and the battery pack including a coupling assisting member for assisting the electrical connection of adjacent battery cells (100). The coupling assisting member is provided with: a conductive plate material (350) fixing part for fixing a conductive plate material (350) that includes a first main surface (351) and a second main surface (352) which are in a front-and-back relationship; a first slit 361 disposed on the first main surface (351) side of the conductive plate material (350); and a secondslit (362) disposed on the second main surface (352) side of the conductive plate material (350). Either the positive or negative lead-out tab of one battery cell (100) passes through the first slit(361) and is conductively connected to the conductive plate material (350) on the first main surface (351). The lead-out tab of the battery cell (100) adjacent to said one battery cell (100), such lead-out tab having a polarity different from that of said one battery cell (100), passes through the second slit (362) and is conductively connected to the conductive plate material (350) on the secondmain surface (352).