An air-intake duct, which is disposed between an air outlet of an air cleaner box constituting an air cleaner and an air inlet of a throttle body constituting a throttle device, is configured to guide air cleaned by the air cleaner to the throttle device. The air-intake duct includes a tubular coupling member including an upstream coupling portion coupled in an air tight manner to the air outlet of the air cleaner box and a downstream coupling portion air-tightly coupled to the air inlet of the throttle body, the coupling member being entirely formed of an elastic rubber material. The air-intake duct also includes an air guide member including a first air inlet configured to take in air therethrough from inside the air cleaner box, a first air outlet configured to discharge the air therethrough toward the throttle body, and a fitting portion fitted to the coupling member.