A miller cycle engine which is provided with a turbocharger for increasing boost pressure and is configured to close an intake valve at a timing earlier or later than the bottom dead center to make a compression ratio lower than an expansion ratio, the miller cycle engine comprising: an intake valve variable unit configured to control a timing to open or close the intake valve; a boost pressure adding device (28, 54, 60) for further adding an additional boost pressure (ΔP) to the boost pressure increased by the turbocharger so as to increase only the boost pressure without involving increase in exhaust pressure, or so as to increase the boost pressure with involving increase in exhaust pressure, the additional boost pressure (ΔP) being larger than the increase in the exhaust pressure; characterized in that the miller cycle engine further comprises: a valve closing timing control unit configured to advance more the timing to close the intake valve as the additional boost pressure (ΔP) added by the boost pressure adding device (28, 54, 60) becomes higher so as to maintain the boost pressure at substantially the same level as a maximum in-cylinder pressure before adding the additional boost pressure (ΔP), wherein the valve closing timing control unit is configured to detect a total boost pressure of the boost pressure provided by the turbocharger and the additional boost pressure (ΔP) added by the boost pressure adding device (28, 54, 60) by means of a boost pressure sensor, and the valve closing timing control unit has a valve closing timing control map in which a valve closing timing for the intake valve is set in accordance with the boost pressure detected by the boost pressure sensor, wherein a relationship between the total boost pressure and an intake valve closing timing is preset in the valve closing timing control map such that a compression stroke is performed along the line of a compression stroke before the additional boost pressure is applied. an intake valve variable unit configured to control a timing to open or close the intake valve; a boost pressure adding device (28, 54, 60) for further adding an additional boost pressure (ΔP) to the boost pressure increased by the turbocharger so as to increase only the boost pressure without involving increase in exhaust pressure, or so as to increase the boost pressure with involving increase in exhaust pressure, the additional boost pressure (ΔP) being larger than the increase in the exhaust pressure; characterized in that the miller cycle engine further comprises: a valve closing timing control unit configured to advance more the timing to close the intake valve as the additional boost pressure (ΔP) added by the boost pressure adding device (28, 54, 60) becomes higher so as to maintain the boost pressure at substantially the same level as a maximum in-cylinder pressure before adding the additional boost pressure (ΔP), wherein the valve closing timing control unit is configured to detect a total boost pressure of the boost pressure provided by the turbocharger and the additional boost pressure (ΔP) added by the boost pressure adding device (28, 54, 60) by means of a boost pressure sensor, and the valve closing timing control unit has a valve closing timing control map in which a valve closing timing for the intake valve is set in accordance with the boost pressure detected by the boost pressure sensor, wherein a relationship between the total boost pressure and an intake valve closing timing is preset in the valve closing timing control map such that a compression stroke is performed along the line of a compression stroke before the additional boost pressure is applied. a valve closing timing control unit configured to advance more the timing to close the intake valve as the additional boost pressure (ΔP) added by the boost pressure adding device (28, 54, 60) becomes higher so as to maintain the boost pressure at substantially the same level as a maximum in-cylinder pressure before adding the additional boost pressure (ΔP), wherein the valve closing timing control unit is configured to detect a total boost pressure of the boost pressure provided by the turbocharger and the additional boost pressure (ΔP) added by the boost pressure adding device (28, 54, 60) by means of a boost pressure sensor, and the valve closing timing control unit has a valve closing timing control map in which a valve closing timing for the intake valve is set in accordance with the boost pressure detected by the boost pressure sensor, wherein a relationship between the total boost pressure and an intake valve closing timing is preset in the valve closing timing control map such that a compression stroke is performed along the line of a compression stroke before the additional boost pressure is applied.