A secondary battery module in which a plurality of chargeable/dischargeable unit cells are arranged at a predetermined interval, wherein a flat plate type cooling plate is interposed between the unit cells, wherein the flat plate type cooling plate is made of aluminum or an aluminum alloy and comprises: a first plate and a second plate, which are coupled to each other, a plurality of cooling sections spaced apart from each other in a longitudinal direction within the cooling plate; a plurality of reinforcement ribs disposed on inner surfaces of the cooling sections; and partition parts that partition the plurality of cooling sections; wherein the reinforcement ribs comprise a plurality of first ribs protruding from the first plate and a plurality of second ribs protruding from the second plate, and the partition parts respectively protrude from inner surfaces of the first and second plates (20a, 20b) so that ends of the partition parts come into contact with each other, characterized in that each of the first and second plates (20a, 20b) independently has a thickness greater 0.2 times to 0.5 times than that of the cooling plate, each of the partition parts has a width of 0.1 mm to 2 mm, each of the first ribs has a width of 0.1 mm to 1 mm and a height corresponding to a thickness greater 0.1 times to 0.3 times than that of the cooling plate, and the first ribs are disposed to be spaced a distance of 0.1 mm to 1 mm from each other, each of the second ribs has a width of 0.1 mm to 1 mm and a height corresponding to a thickness greater 0.1 times to 0.3 times than that of the cooling plate, and the second ribs are disposed to be spaced a distance of 0.1 mm to 1 mm from each other, and ends of the first and second ribs (22a, 22b) are spaced a predetermined distance from each other or the first and second ribs (22a, 22b) are disposed to cross each other. a first plate and a second plate, which are coupled to each other, a plurality of cooling sections spaced apart from each other in a longitudinal direction within the cooling plate; a plurality of reinforcement ribs disposed on inner surfaces of the cooling sections; and partition parts that partition the plurality of cooling sections; wherein the reinforcement ribs comprise a plurality of first ribs protruding from the first plate and a plurality of second ribs protruding from the second plate, and the partition parts respectively protrude from inner surfaces of the first and second plates (20a, 20b) so that ends of the partition parts come into contact with each other, characterized in that each of the first and second plates (20a, 20b) independently has a thickness greater 0.2 times to 0.5 times than that of the cooling plate, each of the partition parts has a width of 0.1 mm to 2 mm, each of the first ribs has a width of 0.1 mm to 1 mm and a height corresponding to a thickness greater 0.1 times to 0.3 times than that of the cooling plate, and the first ribs are disposed to be spaced a distance of 0.1 mm to 1 mm from each other, each of the second ribs has a width of 0.1 mm to 1 mm and a height corresponding to a thickness greater 0.1 times to 0.3 times than that of the cooling plate, and the second ribs are disposed to be spaced a distance of 0.1 mm to 1 mm from each other, and ends of the first and second ribs (22a, 22b) are spaced a predetermined distance from each other or the first and second ribs (22a, 22b) are disposed to cross each other.