A battery cooling apparatus for positively cooling an in-vehicle battery is disclosed. Air that has passed through a cooler (5) is supplied to batteries (1), and only internal air, but not external air, passes through the cooler (5). In this way, the batteries (1) can be cooled without being greatly affected by the disturbances such as the heat of an exhaust pipe and sunlight. Thus, the batteries (1) can be sufficiently cooled without increasing the heat radiation area, i.e. the surface area of the batteries (1). Noise of cooling air flow can be reduced while at the same time suppressing increases in both size and production cost of the battery.