A turbocharged four-stroke cycle engine with a plurality of engine cylinders comprising: an exhaust gas return-flow device for returning to one cylinder of the plurality of engine cylinders, through an exhaust port of the one cylinder, an exhaust gas from an exhaust port of another cylinder of the plurality of engine cylinders; an exhaust-valve lifting and lowering cam, for lifting or lowering an exhaust valve of the one cylinder; and a turbocharger adapted to receive an exhaust gas from each cylinder of the plurality of engine cylinders and which is provided on the exhaust-side of the engine; wherein the cam comprises: a main exhaust lift part for lifting the exhaust valve to discharge the exhaust gas from the one cylinder; and a return-flow lift part (4b, 4b1, 4b2) which is provided on a cam-follower descending side of the cam for delaying a closing timing of the exhaust valve and maintaining the exhaust valve to increase an amount of the exhaust gas returned to the one cylinder from the other cylinder during an opening period of an intake valve regarding the one cylinder, wherein the main exhaust lift part and the return-flow lift part are formed to protrude from a base circle of the cam so as to avoid an interference between the exhaust valve and a piston and increase an overlap between an opening period of the exhaust valve of the one cylinder and an opening period of an exhaust valve of the other cylinder and an amount of the exhaust gas returned to the one cylinder from the other cylinder. an exhaust gas return-flow device for returning to one cylinder of the plurality of engine cylinders, through an exhaust port of the one cylinder, an exhaust gas from an exhaust port of another cylinder of the plurality of engine cylinders; an exhaust-valve lifting and lowering cam, for lifting or lowering an exhaust valve of the one cylinder; and a turbocharger adapted to receive an exhaust gas from each cylinder of the plurality of engine cylinders and which is provided on the exhaust-side of the engine; wherein the cam comprises: a main exhaust lift part for lifting the exhaust valve to discharge the exhaust gas from the one cylinder; and a return-flow lift part (4b, 4b1, 4b2) which is provided on a cam-follower descending side of the cam for delaying a closing timing of the exhaust valve and maintaining the exhaust valve to increase an amount of the exhaust gas returned to the one cylinder from the other cylinder during an opening period of an intake valve regarding the one cylinder, wherein the main exhaust lift part and the return-flow lift part are formed to protrude from a base circle of the cam so as to avoid an interference between the exhaust valve and a piston and increase an overlap between an opening period of the exhaust valve of the one cylinder and an opening period of an exhaust valve of the other cylinder and an amount of the exhaust gas returned to the one cylinder from the other cylinder. a main exhaust lift part for lifting the exhaust valve to discharge the exhaust gas from the one cylinder; and a return-flow lift part (4b, 4b1, 4b2) which is provided on a cam-follower descending side of the cam for delaying a closing timing of the exhaust valve and maintaining the exhaust valve to increase an amount of the exhaust gas returned to the one cylinder from the other cylinder during an opening period of an intake valve regarding the one cylinder, wherein the main exhaust lift part and the return-flow lift part are formed to protrude from a base circle of the cam so as to avoid an interference between the exhaust valve and a piston and increase an overlap between an opening period of the exhaust valve of the one cylinder and an opening period of an exhaust valve of the other cylinder and an amount of the exhaust gas returned to the one cylinder from the other cylinder.