EXHAUST CLEANING DEVICE FOR INTERNAL COMBUSTION ENGINE

In an exhaust purification device of an internal combustion engine, a pair of upstream side NO x storage catalysts 15a 15b storing NO x contained in the exhaust gas when the air-fuel ratio of the inflowing exhaust gas is lean and releasing the stored NO x when the air-fuel ratio of the inflowing exhaust gas becomes the stoichiometric air-fuel ratio or rich are arranged inside an engine exhaust passage. At the downstream side of the upstream side NO x storage catalysts 15a 15b, a downstream side NO x storage catalyst 17 is arranged. The upstream side NO x storage catalysts 15a 15b and downstream side NO x storage catalyst 17 are formed so that the spatial velocity in the downstream side NO x storage catalyst 17 becomes larger than the spatial velocities in the upstream side storage catalysts 15a 15b.