A supercharging system for an engine includes: a cylinder block forming a combustion chamber; an intake manifold connected to the cylinder block to supply ambient air thereto; an exhaust manifold collecting exhaust gas discharged from the combustion chamber and guiding the same to the environment; a third supercharge path connecting an inlet of the intake manifold to the exhaust manifold; and an electric supercharger supplying compressed air to the exhaust manifold through the third supercharge path. Responsiveness of an engine is enhanced and stabilization of the engine is promoted.