An air-conditioning control system for a vehicle includes: an occupant sensing unit determining whether or not there is an occupant inside the vehicle in a state in which a driver exits from the vehicle; a ventilation control unit performing control to allow external air to be introduced into the vehicle, when it is sensed that there is an occupant in the vehicle; and a temperature control unit sensing at least one of an interior temperature of the vehicle or an external temperature at the time of controlling ventilation, and controlling heating or cooling based on the at lease one of the sensed interior temperature or external temperature.