In a central air-conditioning system and method, a distribution mechanism distributes warm air or cool air generated by an air-conditioning unit to a plurality of rooms in a house. A control device controls the distribution mechanism to adjust a temperature of each room. A plurality of room terminals are provided as a device each dedicated to a room. Each room terminal receives an input of a preset temperature for the room and detects temperature of the room, and outputs the received preset temperature and the detected room temperature to the control device. The control device judges whether or not a specified room terminal is mounted in a specified room, based on a transition of control of the distribution mechanism in the specified room and a change in the detected temperature. The control device stops air-conditioning the specified room when judged that the specified room terminal is not mounted in the specified room.