Upper and lower split components include upper and lower concave parts, respectively, forming the inner periphery of an intake pipe. An internal pipe is placed between the upper and lower concave parts. The upper concave part is formed a distance away from the outer periphery of the internal pipe. The outer periphery of the internal pipe is provided with a fitting part fitted into the lower concave part and a sealing part accommodated in an accommodation recess formed in the upper concave part. The inner face of the accommodation recess and the sealing part are formed along the direction of vibration of vibration welding and are in contact with each other.