To prevent damaging caused by excessive revolutions of a high-pressure turbine and a low-pressure turbine by suppressing an increase in number of turbo revolutions at the stop time of exhaust gas recirculation.

The two-stages supercharging system configured to pull out a part of exhaust gas G from an exhaust system on the upstream side of a high-pressure turbine 2 to recirculate it to an intake system on the downstream side of a high-pressure compressor 3, and appropriately stop the recirculation, a high-pressure turbocharger 4 including a variable nozzle turbo, includes: a bypass flow path 11 for bypassing the exhaust gas G from the high-pressure turbine 2 around the low-pressure turbine 5 to guide it downstream of the low-pressure turbine 5; a bypass valve 12 located in the midway of the bypass flow path 11 to open/close the flow path; and a controller 13 for opening nozzle opening of the high-pressure turbine 2 by a necessary amount at the recirculation stop time of the exhaust gas G to reduce exhaust energy of the high-pressure stage, and opening an opening of the bypass valve 12 by a necessary amount to reduce a turbine gas amount of the low-pressure side.