Abstract: An air cleaner, a throttle, a surge tank and air-intake pipes of an intake manifold are combined in a unit and a fuel delivery pipe and fuel injectors are installed in the unit before the unit of an air-intake device is assembled to an internal combustion engine. Cases of the above members are integrally formed thereby to reduce the size of the device and material used for the device. A dusty-side of the air cleaner is disposed under a filter element to prevent dust and water from getting into the clean-side of the filter element when the element is removed to have serviced or inspected.