To provide a method for treating an exhaust gas where dioxin included in the exhaust gas being generated from an arc oven can be positively eliminated from the exhaust gas.

In a method for treating a dust-collection device 4 that is equipped after both systems merge while sucking an exhaust gas generated from an arc oven 11 by a main suction fan 21a being equipped after the both systems merge, and a sub suction fan 31a being equipped after the both systems merge via the main suction system 21 for sucking indirectly from the environment of the arc oven 11 and the sub suction system 31a for directly sucking from the arc oven 11, one or at least two selected from the number of rotation of the main suction fan 21a, that of the sub suction fan 31a, the opening of a main damper being equipped at the main suction system 21, and that of a sub damper being equipped at the sub suction system are controlled.