This device is provided with the NOx catalyst 25 to remove NOx when controlling for richening that an air-fuel ratio of an internal atmosphere is made to be a stoichiometric air-fuel ratio or richen than the stoichimetric air-fuel ratio. 内部雰囲気の空燃比を理論空燃比とし或いは理論空燃比よりもリッチとするリッチ化制御が行われるとNOxを浄化するNOx触媒25を具備する。 - 特許庁