Disclosed is a steel plate cooling system including a plurality of constraining roll pairs that allows a steel plate to pass restrictively therebetween; and an upper cooling apparatus and a lower cooling apparatus that are arranged between the constraining roll pairs so as to be opposed to each other with the steel plate interposed therebetween and have a plurality of spray nozzle rows. The plurality of spray nozzle rows is formed in a plate passing direction of the steel plate, and each of the spray nozzle rows has a plurality of identical spray nozzles lined up in a width direction of the steel plate. When viewed in the plate passing direction, the spray nozzle rows are each classified into an upstream spray nozzle row group located on a relative upstream side and a downstream spray nozzle row group located on a relative downstream side. A number of spray nozzles that belong to the upstream spray nozzle row group is smaller than a number of spray nozzles that belong to the downstream spray nozzle row group.