To provide a battery pack capable of suppressing heat generation due to current flowing through a bus bar and thus suppressing cell deterioration, and improving battery performance by weight reduction. A battery pack 10 includes first to fourth cells 1 to 4 stacked together, each cell including a positive electrode external terminal 12 and a negative electrode external terminal 13 having higher conductivity, and a bus bar 6 that electrically connects the positive electrode external terminal 12 of the second cell 2 and the negative electrode external terminal 13 of the third cell 3, the second and third cells 2 and 3 being disposed side by side next to each other. The bus bar 6 includes a first conductive part 6a connected to the positive electrode external terminal 12 of the second cell 2, a second conductive part 6b connected to the negative electrode external terminal 13 of the third cell 3 and having higher conductivity and higher specific gravity, and a connecting part 6c that connects the first conductive part 6a and the second conductive part 6b. The connecting part 6c is disposed in a first region facing the second cell 2 or in a second region facing the third cell 3.