INTERNAL COMBUSTION ENGINE EXHAUST PURIFYING DEVICE AND EXHAUST PURIFYING METHOD

An internal combustion engine exhaust purifying device is provided that can avoid surging occurring with enrichment of the exhaust A/F. It includes a high-pressure EGR path 6 that recirculates a portion of the exhaust gas upstream of a turbine (81) to an intake manifold (3), a high-pressure EGR control portion (43), a low-pressure EGR path (10) that recirculates a portion of the exhaust gas downstream of the turbine (81) to intake plumbing (2), a low-pressure EGR control portion (44), a NOx purification catalyst (31) that is provided in exhaust plumbing (4), traps NOx under an oxidizing atmosphere, and purifies the NOx trapped under a reducing atmosphere, a NOx purification catalyst reduction control unit (41) that perform reduction control of the exhaust air/fuel ratio, a prediction unit that predicts the occurrence of surging in a turbocharger (8), and an EGR switching portion (45) that selects recirculation control of exhaust gas by way of the low-pressure EGR control portion (43) in a case surging not occurring being predicted, and selects recirculation control of exhaust gas by way of the low-pressure EGR control portion (44) in a case of surging occurring being predicted, during execution of reduction control.