A battery cooling system has a case that forms an internal space surrounded by a plurality of walls to accommodate a plurality of battery cells, a blower accommodated in the case that circulates a fluid for cooling the plurality of battery cells inside of the case, and a passage-along-wall forming member. The passage-along-wall forming member forms passage-along-walls along with and between side walls among the plurality of walls that forms the case. The passage-along-wall forming member has an inflow part where the fluid flowing out of the blower before contacting the battery cells passes when flowing into the passage-along-wall, and an outflow part where the fluid flowed in from the inflow part into the passage-along-wall passes when flowing out from the passage-along-wall.