An engine system includes: an engine main body; an intake pipe; a mass flow sensor that is provided in the intake pipe and outputs a measurement value of an amount of air passing through the intake pipe; an exhaust pipe; a removal device that is provided in the exhaust pipe and removes an air pollutant included in an exhaust gas passing through the exhaust pipe; a recirculation pipe; a recirculation valve that controls a flow rate of the exhaust gas flowing from the recirculation pipe to the intake pipe; a regeneration control unit that closes the recirculation valve; an air amount calculation unit that calculates a theoretical value of an amount of air flowing to the intake side of the engine main body on the basis of a quantity of state of the engine main body during the regeneration process; and a correction unit.