To provider a method for cooling an exhaust gas by which the content of an organic halide in the exhaust gas is efficiently reduced or its generation is inhibited as well as an exhaust gas temperature reducing device.

This method for cooling the exhaust gas containing the organic halide is to cool the exhaust gas at temperatures of 200°C or higher by water spray without generating waste water. The Sauter average diameter of sprayed water droplets is limited to 80 μm or below and the cooling rate of the exhaust gas is set at 100°C/sec or higher, and thus the exhaust gas is cooled down to the temperature level of 180°C or lower.