PURPOSE: To provide an intake air control device for a four-cycle internal combustion engine to improve the intake air filling efficiency of each cylinder as the increase of the number of installed drive mechanisms is suppressed.

CONSTITUTION: Intake air control valves 161-164 and actuators 171-174 are installed to intake air branch pipes 151-154 connected to four cylinders 11-14 of an internal combustion engine 10. Two cylinders 11, 14 and 12, 13, making a set, between which phase differences of a cycle are different from each other in a 360° arc in the rotation angle of the internal combustion engine, and drive circuits 18a and 18b are installed to respective cylinder sets and controlled by a control part 19. Thus, an intake air control valve is opened during the early stage of an exhaust stroke and by closing an intake valve during opening of an intake air valve, intake air filling efficiency is improved, incurring of the pumping loss of a suction stroke is reduced, and spitting right before closing of the intake air valve is prevented from occurring.