A plated steel sheet cooling apparatus comprising: a spraying unit opposing a driving steel sheet and spraying a cooling fluid; the plated steel sheet cooling apparatus being characterized by further comprising a spraying width varying unit varying a spraying width of the cooling fluid to correspond to a width of the steel sheet, and installed outside of the spraying unit so as not to interfere with an spraying flow path of the cooling fluid, wherein the spraying width varying unit includes: a plurality of nozzle shield plates installed in a front of the spraying unit, and varying the spraying width of the cooling fluid while being moved far from and near to each other on both sides; and a plate driving unit moving the plurality of nozzle shield plates, wherein each nozzle shield plate has a rack gear, and the plate driving unit includes: two rotary shafts connected to the plurality of nozzle shield plates, respectively, the two rotary shafts being disposed on both sides of the spraying unit and having a plurality of pinion gears engaged with the rack gears; and a rotary driving member rotating the rotary shaft, wherein the rotary driving member includes: lateral gearboxes mounted on upper ends of the respective rotary shafts and disposed to be two lateral gearboxes thereon; a rotary driving motor installed on the spraying unit; a central gearbox to which a motor shaft of the rotary driving motor is connected; and two connection bars in which one end is connected to the lateral gearbox and the other end is connected to the central gearbox. a spraying unit opposing a driving steel sheet and spraying a cooling fluid; the plated steel sheet cooling apparatus being characterized by further comprising a spraying width varying unit varying a spraying width of the cooling fluid to correspond to a width of the steel sheet, and installed outside of the spraying unit so as not to interfere with an spraying flow path of the cooling fluid, wherein the spraying width varying unit includes: a plurality of nozzle shield plates installed in a front of the spraying unit, and varying the spraying width of the cooling fluid while being moved far from and near to each other on both sides; and a plate driving unit moving the plurality of nozzle shield plates, wherein each nozzle shield plate has a rack gear, and the plate driving unit includes: two rotary shafts connected to the plurality of nozzle shield plates, respectively, the two rotary shafts being disposed on both sides of the spraying unit and having a plurality of pinion gears engaged with the rack gears; and a rotary driving member rotating the rotary shaft, wherein the rotary driving member includes: lateral gearboxes mounted on upper ends of the respective rotary shafts and disposed to be two lateral gearboxes thereon; a rotary driving motor installed on the spraying unit; a central gearbox to which a motor shaft of the rotary driving motor is connected; and two connection bars in which one end is connected to the lateral gearbox and the other end is connected to the central gearbox. a plurality of nozzle shield plates installed in a front of the spraying unit, and varying the spraying width of the cooling fluid while being moved far from and near to each other on both sides; and a plate driving unit moving the plurality of nozzle shield plates, wherein each nozzle shield plate has a rack gear, and the plate driving unit includes: two rotary shafts connected to the plurality of nozzle shield plates, respectively, the two rotary shafts being disposed on both sides of the spraying unit and having a plurality of pinion gears engaged with the rack gears; and a rotary driving member rotating the rotary shaft, wherein the rotary driving member includes: lateral gearboxes mounted on upper ends of the respective rotary shafts and disposed to be two lateral gearboxes thereon; a rotary driving motor installed on the spraying unit; a central gearbox to which a motor shaft of the rotary driving motor is connected; and two connection bars in which one end is connected to the lateral gearbox and the other end is connected to the central gearbox. two rotary shafts connected to the plurality of nozzle shield plates, respectively, the two rotary shafts being disposed on both sides of the spraying unit and having a plurality of pinion gears engaged with the rack gears; and a rotary driving member rotating the rotary shaft, wherein the rotary driving member includes: lateral gearboxes mounted on upper ends of the respective rotary shafts and disposed to be two lateral gearboxes thereon; a rotary driving motor installed on the spraying unit; a central gearbox to which a motor shaft of the rotary driving motor is connected; and two connection bars in which one end is connected to the lateral gearbox and the other end is connected to the central gearbox. lateral gearboxes mounted on upper ends of the respective rotary shafts and disposed to be two lateral gearboxes thereon; a rotary driving motor installed on the spraying unit; a central gearbox to which a motor shaft of the rotary driving motor is connected; and two connection bars in which one end is connected to the lateral gearbox and the other end is connected to the central gearbox.