POWER SUPPLY DEVICE

A power supply device disclosed by the present specification includes: a first power storage element group that has a pair of first external terminals having different polarities, and includes a plurality of power storage elements; and a second power storage element group that has a pair of second external terminals having different polarities, and includes a plurality of power storage elements. The first power storage element group and the second power storage element group are arranged adjacent to each other in a front-rear direction, the first external terminals are provided at the front edge on the second power storage element group side of the first power storage element group, and the second external terminals are arranged to be adjacent to the first external terminals at a rear edge on the first power storage element group side of the second power storage element group.