A cover 1b of a battery pack case has an intake port and an exhaust port 31. With in the battery pack case, battery accommodation sections respectively accommodate battery modules and a junction box accommodation section. A supply flow path and an exhaust flow path are provided at ends of each of the battery accommodation section. A guide is provided between the cover and the battery modules accommodated in the battery accommodation portions. The guide and a lower surface of the cover define a distribution flow path. The air introduced from the intake port flows to the exhaust port through the distribution flow path, supply flow paths, clearances between battery cells, exhaust flow paths, and exhaust port. The battery cells are efficiently cooled.