BATTERY PACK

A battery pack includes unit cells and holders for sandwiching the unit cells. The holder includes a holding portion which holds the unit cell such that an electrode of the unit cell projects from between the holder and another holder sandwiching the unit cell, and a plurality of projecting portions which project in a direction in which the electrode projects from the holding portion and face each other across the electrode projecting from the holding portion. The projecting portion includes a passage which is formed along a direction, in which the unit cell is sandwiched, and is configured to flow fluid, and an opening which communicates with the and is open toward the electrode projecting from the holding portion.