A power source apparatus comprising: a plurality of batteries; a chassis having an inner space surrounded by a plurality of wall surfaces and storing the batteries in the inner space; and a blower to blow air, wherein the power source apparatus further comprises: a blow path formed between the wall surface and the batteries, the blow path being configured to flow the air that has been blown from the blower to be introduced to the batteries; the plurality of wall surfaces include: a first wall surface disposed on a first side of the batteries; and a second wall surface connected to the first wall surface and extended toward a side opposite to the first side of the batteries, wherein an air introduction path is formed between the first wall surface and the batteries and serves as a part of the blow path, the air introduction path being configured to introduce the air to the batteries, wherein a flow path is formed between the second wall surface and the batteries and serves as a part of the blow path, the flow path being configured to introduce the air to the air introduction path, the air being blown from the blower, wherein a cross-sectional area of the flow path is smaller than a cross-sectional area of the air introduction path, wherein an inner wall surface including the wall surfaces constituting the blow path includes a direction changing portion configured to change a direction of the blow path, and wherein a heat-insulating portion is disposed at least on a portion including the direction changing portion in the inner wall surface and on another portion including the second wall surface constituting the flow path, the heat-insulating portion being constituted by applying a heat-insulating member on the inner wall surface a plurality of batteries; a chassis having an inner space surrounded by a plurality of wall surfaces and storing the batteries in the inner space; and a blower to blow air, wherein the power source apparatus further comprises: a blow path formed between the wall surface and the batteries, the blow path being configured to flow the air that has been blown from the blower to be introduced to the batteries; the plurality of wall surfaces include: a first wall surface disposed on a first side of the batteries; and a second wall surface connected to the first wall surface and extended toward a side opposite to the first side of the batteries, wherein an air introduction path is formed between the first wall surface and the batteries and serves as a part of the blow path, the air introduction path being configured to introduce the air to the batteries, wherein a flow path is formed between the second wall surface and the batteries and serves as a part of the blow path, the flow path being configured to introduce the air to the air introduction path, the air being blown from the blower, wherein a cross-sectional area of the flow path is smaller than a cross-sectional area of the air introduction path, wherein an inner wall surface including the wall surfaces constituting the blow path includes a direction changing portion configured to change a direction of the blow path, and wherein a heat-insulating portion is disposed at least on a portion including the direction changing portion in the inner wall surface and on another portion including the second wall surface constituting the flow path, the heat-insulating portion being constituted by applying a heat-insulating member on the inner wall surface a blow path formed between the wall surface and the batteries, the blow path being configured to flow the air that has been blown from the blower to be introduced to the batteries; the plurality of wall surfaces include: a first wall surface disposed on a first side of the batteries; and a second wall surface connected to the first wall surface and extended toward a side opposite to the first side of the batteries, a first wall surface disposed on a first side of the batteries; and a second wall surface connected to the first wall surface and extended toward a side opposite to the first side of the batteries, wherein an air introduction path is formed between the first wall surface and the batteries and serves as a part of the blow path, the air introduction path being configured to introduce the air to the batteries, wherein a flow path is formed between the second wall surface and the batteries and serves as a part of the blow path, the flow path being configured to introduce the air to the air introduction path, the air being blown from the blower, wherein a cross-sectional area of the flow path is smaller than a cross-sectional area of the air introduction path, wherein an inner wall surface including the wall surfaces constituting the blow path includes a direction changing portion configured to change a direction of the blow path, and wherein a heat-insulating portion is disposed at least on a portion including the direction changing portion in the inner wall surface and on another portion including the second wall surface constituting the flow path, the heat-insulating portion being constituted by applying a heat-insulating member on the inner wall surface