Disclosed is a battery cooling system having a main frame for defining a structure of a battery rack; a space dividing frame for dividing the inside of the main frame into a plurality of levels; a battery module located inside the main frame and supported by the space dividing frame; a pair of refrigerant guide plates respectively installed at the upper and lower ends of the battery module and installed to be inclined in the same direction with predetermined angles with respect to the upper and lower surfaces thereof; and side panels coupled to the sides of the main frame and having a channel slit formed in at least a part thereof.