PURPOSE: To eliminate the loss of a dust collecting function by reducing the change width of the temperature of exhaust gas fed to a bag filter type dust collector in an exhaust gas treating apparatus in which dust contained in the exhaust gas of an arc furnace is collected by the collector.

CONSTITUTION: An exhaust gas treating apparatus for an arc furnace 1 quenches the exhaust gas exhausted from the furnace by pouring water spray via a spray tower 6, passes the gas through a bag filter type dust collector to collect the dust and exhausts it into the atmosphere, and comprises a thermal storage material 9 which alternately store heat and radiate heat according to the temperature of the gas and is lined on the inner surface of the tower 6.