A cooling apparatus of a steel sheet, which is excellent in discharging water without hindering the movement of a steel sheet, is disposed on a lower process side of a final stand in a row of hot finish rolling mills. The apparatus includes a plurality of cooling nozzles arranged to cool a steel sheet transported on transporting rolls, wherein the cooling nozzles are arranged on upper and lower surface sides of an area in which the steel sheet passes. A lower surface guide is arranged on the lower surface side with the lower surface guide comprising inlet holes through which cooling water sprayed from the cooling nozzles on the lower surface side passes and outlet holes through which the cooling water passes, dropping downwardly to be discharged. The inlet holes and the outlet holes are arranged alternately in a moving direction of the steel sheet.