Abstract: A control device is a control device of an engine system including an engine, an oxidation catalyst provided in an exhaust passage of the engine, and a filter configured to collect soot within the exhaust passage, the soot being contained in exhaust gas of the engine, the control device including: an ash accumulation amount estimation unit configured to estimate an ash amount accumulated in the filter; and a regeneration control unit configured to control regeneration of the filter when the ash amount is equal to or less than a predetermined threshold value so that a predetermined amount of the soot remains in the filter, and control regeneration of the filter when the ash amount is greater than the threshold value so that the remaining amount of the soot in the filter is less than the predetermined amount.