1. A method for regenerating an NOx removal catalyst, characterized in that the method comprises:mixing an abrasive with a gas in a mixing part connected to an upstream portion of an upstream fixing member, by the mediation of an upstream connecting member, wherein the upstream fixing member is connected to one end of a member to be ground which is formed of an NOx removal catalyst, the upstream fixing member includes an expanded part which has a cross-sectional area larger than that of the NOx removal catalyst and has a screen member having a predetermined sieve opening of #8 to #40 disposed in the expanded part on the NOx removal catalyst side, the upstream connecting member includes a flow path which has a cross-sectional area smaller than that of the expanded part,
transferring the abrasive which has been mixed with the gas from the mixing part, through suction by a dust-collecting part, to the upstream fixing member,
reducing the flow rate of the mixture of the gas and the abrasive in the expanded part, to thereby temporarily retain the mixture in the expanded part,
subsequently, causing the mixture to pass through through-holes of the NOx removal catalyst and a downstream fixing member, to thereby grind the inner walls of the through-holes, and
subsequently, collecting dust by the dust-collecting part via a classification part,
wherein the downstream fixing member is connected to the other end of the NOx removal catalyst, the downstream fixing member including a flow path which has a fixed cross-sectional area over a predetermined length from a fixing end of NOx removal catalyst, and
the classification part and the dust-collecting part are connected to a downstream portion of the downstream fixing member, by the mediation of a downstream connecting member connected to a connecting part which is located on the downstream portion of the downstream fixing member and has a cross-sectional area smaller than the fixed cross-sectional area of the downstream fixing member, the classification part being adapted to separate the abrasive which has passed through through-holes of the NOx removal catalyst from a ground matter generated through grinding by the abrasive, and the dust-collecting part being adapted to absorb the gas in the mixing part via the classification part, and
wherein the member to be ground comprises an NOx removal catalyst and a dummy cell having a separate body which does not belong to the NOx removal catalyst for regenerating and is disposed around the outer surface of the catalyst, and the dummy cell has through-holes where the mixture is to be passed.