An engine with a boosting system is provided, which includes a turbocharger including a compressor provided in an intake passage of the engine and configured to boost intake air to be supplied to the engine, and a turbine provided in an exhaust passage of the engine. The engine includes an electric supercharger provided in the intake passage downstream of the compressor and configured to operate when the engine operates in a low-speed range, an emission control device provided in the exhaust passage upstream of the turbine and configured to purify exhaust gas discharged from the engine, and an EGR system having a passage connecting a part of the intake passage between the compressor and the electric supercharger to a part of the exhaust passage between the emission control device and the turbine, and configured to recirculate a part of the exhaust gas to the intake passage as EGR gas.