Exhaust gas purifier for internal combustion engine

An exhaust gas purifier (26) has DPFs (19A, 19B) to collect and remove PM from exhaust gases passing through exhaust passages (11A, 11B), and ECU (25). ECU (25) estimates PM emission amounts to respective DPFs (19A, 19B), based on air-fuel ratios of the exhaust gases detected by air-fuel ratio sensors (22A, 22B) and exhaust temperatures detected by exhaust temperature sensors (20A, 20B). When a difference between PM emission amount estimates for DPFs (19A, 19B) is larger than a threshold, ECU (25) gives offsets to a fuel injection quantity of respective cylinder groups (3A, 3B) so as to decrease a difference between PM emission amounts to DPFs (19A, 19B). ECU (25) controls each of fuel injection valves (4) in the cylinder groups (3A, 3B) so as to perform main injection according to the offset fuel injection quantities.