A power source apparatus includes a plurality of batteries, a blower having a blowing portion arranged on one side of the batteries, the blower being configured to blow air from the blowing portion, a chassis having an inner space surrounded by a plurality of wall surfaces that include a first wall surface and a second wall surface and storing the batteries in the inner space. The power source apparatus includes an air introduction path formed between the first wall surface and the batteries, the air introduction path being configured to introduce the air to the batteries, and a flow path formed between the second wall surface and the batteries, the flow path being configured to introduce the air blown from the blower to the air introduction path, the air introduction path having at least partially a first cross-sectional area larger than a second cross-sectional area of the flow path.