In an air conditioning case of an air conditioner, an air mixing chamber, a warm-air bypass passage, a first warm-air passage and a second warm-air passage are provided. The warm-air bypass passage is located in a part of space, in which the air mixing chamber is provided, and the second warm-air passage is located at an opposite side of the first warm-air passage with respect to the air mixing chamber. The warm air flowing in the warm-air bypass passage makes a U-turn at the second warm-air passage and flows toward the air mixing chamber. Therefore, in the air mixing chamber, the cool air is inserted between the warm air from the first warm-air bypass passage and the warm air from the second warm-air passage, from two sides of the cool air.