To provide a method for regenerating a dioxin decomposition catalyst which can cope with the degradation of activity due to the deposition of copper and/or iron, does not require thermal sintering and is advantageous economically.

In this method for regenerating the dioxin decomposition catalyst that is used for decomposing and removing dioxins in exhaust gas, the used dioxin decomposition catalyst is washed in an acidic aqueous solution of pH at 1-6. In a more preferable embodiment, a washing time in the acidic aqueous solution is 0.2 to 10 times of the time T (minute)calculated by the experimental relation (1).