At least two exhaust holes are formed in an atomizing nozzle of an apparatus for spraying an air-water mist for cooling which is used in continuous metal casting. The respective spraying mist streams from the exhaust holes cross each other before they reach the surface of a cast strand and are diffused forwardly due to the influence of the kinetic energy which is directed in the spraying direction after they crossed, so that they sufficiently enter the region between the surfaces of guide rollers and cast strand, thereby directly spraying the air-water mist over almost the entire region of the surface of the cast strand. In addition, a header is disposed in parallel to the guide rollers and a plurality of water branching pipes are attached in line to the header in the longitudinal direction thereof. The inner diameter of these water branching pipes are set to be sequentially smaller toward the lower stage. The back pressures of the atomizing nozzles are reduced by causing pressure losses in the water branching pipes coupled to the atomizing nozzles, thereby spraying a uniform flow rate of the water from each water branching pipe.