An air conditioning control device and a method thereof are provided, and the air conditioning control method includes the following steps. A plurality of predetermined state information and a current state information are generated according to environment states of a physical space, and a target state information is selected form the plurality of predetermined state information according to a minimum energy consumption. Moreover, the current state information and the target state information are utilized to generate a current effective temperature value and a target effective temperature value, and a set temperature value and a return-air temperature value are extracted from an air conditioning controller. The current effective temperature value, the target effective temperature value, the set temperature value and the return-air temperature value are utilized to execute fuzzy inference to generate a temperature fine-tuning value. The temperature fine-tuning value is utilized to adjust the set temperature value.