A supercharging apparatus for an internal combustion engine comprises an intake air passage communicating with a cylinder of an engine through an intake valve; a mechanical supercharger provided in the intake air passage; a variable valve timing mechanism for varying a closing timing of the intake valve with respect to a bottom dead center of an engine piston; a control unit for controlling the variable valve timing mechanism in accordance with an engine speed at least in a supercharging region wherein the mechanical supercharger is operative to supply supercharged air into the cylinder, in such a manner that the closing timing of the intake valve is switched between an advanced timing and a delayed timing; and an assist intake system for causing a dynamic supercharging effect in the intake air passage when the closing timing of the intake valve is switched to the delayed timing, thereby assisting the mechanical supercharger in a low engine operational region.