An air conditioner for a vehicle includes a refrigeration cycle having a variable capacity compressor, a condenser, an expansion valve, and an evaporator; a duct in which the evaporator is arranged; an air switching unit arranged on an upstream side of the duct and configured to switch outside air and inside air from one to the other; an air outlet arranged on a downstream side of the duct and communicating with an interior of the vehicle; and a control unit configured to control a discharge of the compressor. The control unit controls the compressor to provide a maximum capacity if the difference between a vehicle interior temperature and an ambient temperature is higher than a predetermined value and if the air switching unit is switched from a recirculation mode to a fresh air mode.