A battery pack in which an air-suction portion with an air inlet and an air-exhaust portion with an air outlet are formed in a battery pack body including a battery region accommodating a plurality of battery modules therein and an electrical apparatus region accommodating an electrical apparatus therein, the electrical apparatus region dividing the battery region in a longitudinal direction thereof, wherein the battery pack body includes a box-shaped battery pack case whose upper surface is opened, and a battery pack cover which closes the opening, a first side air flow path for allowing air sucked through the air-suction portion in a first flowing direction is formed between one of opposite sidewalls of the battery pack case and opposing battery modules, the first side air flow path being in communication with the battery region, the electrical apparatus region includes a box-shaped electrical apparatus cover which covers at least a portion of the electrical apparatus, and the box-shaped electrical apparatus cover includes (i) a first side surface that is opposed to said one of the sidewalls of the battery pack case and constitutes a part of the first side air flow path, and (ii) a second side surface which constitutes an air flow path for allowing air in a second flowing direction toward the other of the opposite sidewalls of the battery pack case, the air flow path intersecting with the first side air flow path, air sucked through the air-suction portion being branched at the intersection in such a manner that the branched air flows to battery modules that are disposed downstream of the electrical apparatus region. wherein the battery pack body includes a box-shaped battery pack case whose upper surface is opened, and a battery pack cover which closes the opening, a first side air flow path for allowing air sucked through the air-suction portion in a first flowing direction is formed between one of opposite sidewalls of the battery pack case and opposing battery modules, the first side air flow path being in communication with the battery region, the electrical apparatus region includes a box-shaped electrical apparatus cover which covers at least a portion of the electrical apparatus, and the box-shaped electrical apparatus cover includes (i) a first side surface that is opposed to said one of the sidewalls of the battery pack case and constitutes a part of the first side air flow path, and (ii) a second side surface which constitutes an air flow path for allowing air in a second flowing direction toward the other of the opposite sidewalls of the battery pack case, the air flow path intersecting with the first side air flow path, air sucked through the air-suction portion being branched at the intersection in such a manner that the branched air flows to battery modules that are disposed downstream of the electrical apparatus region. (i) a first side surface that is opposed to said one of the sidewalls of the battery pack case and constitutes a part of the first side air flow path, and (ii) a second side surface which constitutes an air flow path for allowing air in a second flowing direction toward the other of the opposite sidewalls of the battery pack case, the air flow path intersecting with the first side air flow path, air sucked through the air-suction portion being branched at the intersection in such a manner that the branched air flows to battery modules that are disposed downstream of the electrical apparatus region.