PURPOSE: To prevent air pollution effectually, by forming an enclosed casing at an upper portion of a smokestack, and disposing a flow dividing plate having a water sprinkling means at an upper portion in the enclosed casing.

CONSTITUTION: An enclosed casing 26 is formed at a portion of a smokestack 22, and a flow dividing plate 37 having at an upper portion thereof an overflow tank 35 functioning as a water sprinkling means is disposed in the enclosed casing 26. With such an arrangement, incompletely burnt substances such as soot and sulfur oxides contained in smoky exhaust gas are absorbed and removed by water when the exhaust gas flow is divided by the flow dividing plate 37 and the incompletely burnt substances come into contact with water discharged from the water sprinkling means. Therefore, it is enabled to prevent air pollution effectually.