To suppress the frosting of an evaporator in closing at least one passage in an air conditioner with the downstream side of the evaporator partitioned into a plurality of passages.

A gap 9 having a width of 4 mm is provided between a partitioning member 8 provided in the air downstream side of an evaporator 3 and the evaporator 3. Thus, even if a rear seat side passage 7 is closed, air passing through the evaporator 3 in the rear seat side passage 7 is caused to flow through the gap 9 to a driver's seat side passage 5 and a front passenger seat side passage 6. Therefore, since air continues to flow to the evaporator 3 in the rear seat side passage 7 even if the rear seat side passage 7 is closed, the frosting of the evaporator 3 is suppressed.