An air duct for vehicle air conditioning, includes a duct body defining a passage, and a passage dividing wall for dividing an interior of the duct body into a first passage and a second passage. In the air duct, the width of the duct body in an arrangement direction of the first and second passages in a bending section is larger than the width of the duct body in upstream-side and downstream side straight sections adjacent to the bending section, so as to increase a passage length difference (L1−L2) between the first passage and the second passage. Accordingly, the air duct has a structure capable of reducing the duct width while obtaining a desired passage length difference between the first passage and the second passage.