To provide an intake air flow control device 1 securing a high-tumble flow by maintaining a main flow rate at a constant value or more, without increasing a bypass flow rate while expanding a side clearance.

The intake air flow control device 1 is equipped with: an approximately square cylindrical valve housing 8 incorporated in along an inner wall surface of each intake air flow passage 3 of an intake manifold 2 and where the intake air flow passage 3 is formed in an inner part; an intake air flow switching valve 4 composed of a valve shaft 5 installed between right and left side walls of the valve housing 8, and a valve 9 fitted to the valve shaft 5 and opens/closes the intake air flow passage 3; a drive pin shaft 6 which connects the valve shafts 5 of each intake air flow switching valve 4 with each other and rotationally drives; and an actuator 7 which is directly connected to the drive shaft 6, and openably/closably drives each intake air flow switching valve 4. The width between the right and left valve sides of the valve 9 is set larger than the width between the right and left side walls of the intake air flow passage 3 of the intake manifold 2 upstream of the valve 9.