An engine may include an engine including combustion chambers, an intake line connected to the plurality of combustion chambers and through which outside air supplied to the combustion chamber flows, an intake manifold connected to an intake side of the combustion chamber, an exhaust manifold connected to an exhaust side of the combustion chamber, an exhaust line connected to the exhaust manifold, a turbocharger including a compressor mounted in the intake line, and a turbine rotating in association with the compressor and connected to the exhaust manifold and the exhaust line, a wastgate passage bypassing the turbine from the exhaust manifold, an electric supercharger connected to the compressor of the turbocharger by the intake line, a power device electrically-connected to the electric supercharger and configured for supplying electric power to the electric supercharger or absorbing and storing electric power generated by the electric supercharger, and a controller for controlling the operation of the power device and the electric supercharger according to rotation speed of the engine.