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. <EOS>