Power source apparatus to supply electric power and vehicle equipped with the power source apparatus

The power source apparatus to supply electric power is provided with a battery block 3 having a plurality of rectangular batteries 1 disposed in a stacked configuration with conducting external cases 11 insulated by insulating layers 2, a cooling plate 4 disposed at the bottom of the battery block 3 in a manner that thermally couples with each rectangular battery 1 and forcibly cools each battery 1 from its bottom surface, and a cooling mechanism 5 that cools the cooling plate 4. The insulating layers 2 are formed as a unit with each external case 11 and have a fit-together structure that enables stacking in fixed positions. Each rectangular battery 1 and insulating layers 2 form a single-piece battery module 10, and a battery block 3 is made up of a plurality of stacked battery modules 10.