An air-intake device includes a throttle valve pivotally movable around a shaft connected to one end of the throttle valve and an airflow passage formed in the intake air passage above an upper end of the throttle valve. In a region where an amount of intake air is small (i.e., in a region where an opening-degree of the throttle valve is small), an amount of intake air passing through the airflow passage is precisely controlled. In the same region, a high-speed airflow is generated in the airflow passage thereby to formulate a uniform air-fuel mixture in a combustion chamber of an internal combustion engine. These functions are easily realized by simply adding a member for forming the airflow passage to a throttle valve unit disposed in the intake air passage.