Intake system for internal combustion engine

An intake system (100) for an internal combustion engine includes a throttle-side intake tube (1), an external gas introducing port (11) introducing an external gas into at least one of the throttle-side intake tube (1) and a surge tank (2), and a plate portion (40) provided inside the mentioned at least one of the throttle-side intake tube (1) and the surge tank (2) being in communication with the external gas introducing port (11) and in a region on an axis line (AL) of the external gas introducing port (11) at a center portion of a fluid path cross-section having a distance from a vicinity of an outer periphery portion of the fluid path cross-section, the plate portion (40) restraining the external gas that is introduced from the external gas introducing port (11) from flowing to the vicinity of the outer periphery portion of the fluid path cross-section by blocking the external gas at the center portion of the fluid path cross-section.