To appropriately detect deterioration of a catalyst, in an exhaust control device for an internal combustion engine performing an exhaust control with respect to the internal combustion engine having a plurality of cylinder groups.
The exhaust control device is suitably used for the exhaust control with respect to the internal combustion engine having first and second cylinder groups. A first catalyst and a second catalyst are respectively disposed on an exhaust passage each connected to the first cylinder group and the second cylinder group. A first control valve is disposed on a communication passage for connecting an exhaust passage upstream of the first catalyst and an exhaust passage upstream of the second catalyst. A first valve control means sets the first control valve to be closed when detecting deterioration states of the first and second catalysts. Therefore, the deterioration states of both first and second catalyst is accurately detected, and degradation in fuel economy caused by the deterioration detection is effectively suppressed since their deterioration states can be detected at the same time.
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