Air conditioner for vehicle

An air conditioner for a vehicle, comprising:

• an air-conditioning case having a heat exchanger, and a first door and a second door disposed inside the air-conditioning case and configured to slidingly adjust a degree of opening of an air passageway,
• a first shaft having a first gear part geared with gear teeth formed on the first door,
• a second shaft having a second gear part geared with gear teeth formed on the second door,
• a rack gear for connecting and interlocking the first shaft and the second shaft,
• wherein the first gear part comprises an first operation gear part engaged with the gear teeth of the first door and a misassembly preventing part comprising a first changing part which is thicker than the first operation gear part and a concave groove dented in an axial direction from the first changing part such that a protrusion formed on the door is inserted into the concave groove,
• wherein a nonoperation part having a thickness greater than that of the first operation gear part is caught by the gear teeth of the first door to limit sliding and becomes a starting point of sliding,
• wherein the nonoperation part is formed on an opposite side of the first gear part from the misassembly preventing part, and
• wherein the protrusion formed on the first door is thicker than the gear teeth of the first door.