The amount of air to be introduced is controlled for each cylinder, whereby it is intended to make it possible to control the torque generated in each cylinder, perform an ultra-lean burn operation, purify the exhaust gas, and increase the output of an engine. An air flow control valve adapted to be on-off controlled in accordance with an operated quantity of an accelerator pedal is disposed in each branch pipe or intake port. The air flow control valve may be a throttle valve disposed in each branch pipe or it may be a variable intake valve for opening and closing the intake port.