To provide a method for starting an exhaust gas treatment device that improves the durability of an electrode and facilitates maintenance of the exhaust gas treatment device by stably generating plasma from an initial state in a short time.

The method for starting an exhaust gas treatment device for treating exhaust gas introduced in a reaction tube by dissolving the gas by plasma generated between electrodes disposed in the reaction tube, includes generating plasma between the electrodes 2 and 3 after power distribution to the electrodes 2 and 3.