An air intake duct includes a peripheral wall, which is formed by a compressed fiber portion made of a compression molded fiber material. The compressed fiber portion includes high-compression portions having a high compression ratio and low-compression portions having a relatively low compression ratio. The high-compression portions include circumferentially extending sections. Each circumferentially extending section is located in a plane that is perpendicular to an extension direction of the peripheral wall with part of the circumferentially extending section disposed between the low-compression portions. Each circumferentially extending section extends continuously over the entire circumference of the peripheral wall.