An intake port structure for an internal combustion engine comprising: an intake air passage including a collector passageway and a pair of first and second branching passageways (3, 4) branching from the collector passageway toward first and second intake valve openings, respectively; a fuel injector arranged in the collector passageway of the intake air passage to inject a fuel stream into intake air that flows through the intake air passage; and an intake air flow impact section formed on a crotch portion between the first and second branching passageways (3, 4), the intake air flow impact section being configured and arranged such that a portion of the intake air flowing in the intake passage collides against the intake air flow impact section to laterally disperse the intake air into the first and second branching passageways (3, 4) at areas encompassed by imaginary tubes projected from the first and second intake valve openings in a direction parallel to a center combustion chamber axis, wherein the intake air flow impact section includes at least a first generally flat surface, wherein said first generally flat surface of the intake air flow impact section is oriented substantially perpendicular to a plane passing through the combustion chamber axis and a center axis of the collector passageway, the first generally flat surface is formed substantially parallel to a plane encompassing the first and second intake valve openings, wherein the fuel injector is disposed in the collector passageway such that a center axis of the fuel injector is disposed in a plane including the combustion chamber axis and the center axis of the collector passageway, and the fuel injector includes a two-way fuel injection valve configured and arranged to inject fuel in two paths from the collector passageway toward the first and second branching passageways (3, 4), characterized in that the intake air flow impact section includes at least a second generally flat surface that is oriented in a plane substantially perpendicular to a plane encompassing the first and second intake valve openings, wherein said second generally flat surface of the intake air flow impact section is oriented substantially perpendicular to a plane passing through the combustion chamber axis and a center axis of the collector passageway. an intake air passage including a collector passageway and a pair of first and second branching passageways (3, 4) branching from the collector passageway toward first and second intake valve openings, respectively; a fuel injector arranged in the collector passageway of the intake air passage to inject a fuel stream into intake air that flows through the intake air passage; and an intake air flow impact section formed on a crotch portion between the first and second branching passageways (3, 4), the intake air flow impact section being configured and arranged such that a portion of the intake air flowing in the intake passage collides against the intake air flow impact section to laterally disperse the intake air into the first and second branching passageways (3, 4) at areas encompassed by imaginary tubes projected from the first and second intake valve openings in a direction parallel to a center combustion chamber axis, wherein the intake air flow impact section includes at least a first generally flat surface, wherein said first generally flat surface of the intake air flow impact section is oriented substantially perpendicular to a plane passing through the combustion chamber axis and a center axis of the collector passageway, the first generally flat surface is formed substantially parallel to a plane encompassing the first and second intake valve openings, wherein the fuel injector is disposed in the collector passageway such that a center axis of the fuel injector is disposed in a plane including the combustion chamber axis and the center axis of the collector passageway, and the fuel injector includes a two-way fuel injection valve configured and arranged to inject fuel in two paths from the collector passageway toward the first and second branching passageways (3, 4), characterized in that the intake air flow impact section includes at least a second generally flat surface that is oriented in a plane substantially perpendicular to a plane encompassing the first and second intake valve openings, wherein said second generally flat surface of the intake air flow impact section is oriented substantially perpendicular to a plane passing through the combustion chamber axis and a center axis of the collector passageway.