The regeneration control system is provided that conducts a regeneration processing for oxidizing particulate matter collected in the diesel particulate filter (DPF) whereby the regeneration processing can be performed efficiently while avoiding the melting of the diesel particulate filter. The regeneration control system is provided for an exhaust filter wherein at least one parameter selected from among the target filter temperature, target exhaust air-fuel ratio, and target regeneration control time in the DPF regeneration is varied in accordance with the amount of particulate matter when the exhaust air-fuel ratio and exhaust temperature are controlled to perform the DPF regeneration by staged retarded combustion, which is composed of preliminary combustion that is performed at least once in the vicinity of the top dead center, and main combustion that causes the generation of main torque and is initiated after the preliminary combustion has been completed.