Air conditioner for vehicle

The present invention relates to an air conditioner for a vehicle including: a plate member (150) slidably operating inside an air-conditioning case (110) to control the degree of opening of air outflow ports (116) or air passageways (110e) inside the air-conditioning case (110); a gear shaft (140) for operating the plate member (150), and separation preventing means (153) formed on rail portions (151) of the plate member (150) interlocking with the gear shaft (140). According to the present invention, the gear portions (141) of the gear shaft (140) can be smoothly interlocked with the gear holes (152) formed on the rail portions (151) of the plate member (150) and it is prevented that the gear portions (141) of the gear shaft (140) in interlock with the gear holes (152) of the rail portions (151) are separated from the gear holes (152) or mislocated.