A battery pack of the present invention includes a stacked body of a plurality of solid state battery cells, end plates connected to both ends of the stacked body in a stacking direction, respectively, first wall members connected to the end plates on the both ends via a first self-centering mechanism, respectively, and a support member configured to support the first wall member, the first self-centering mechanism being constituted by a spherical member and two plate-shaped members slidable on a surface of the spherical member, one of the plate-shaped member being connected to the end plate, and other one of the plate-shaped member being connected to the first wall member.