A device and method for executing a reserved function using time information extracted from a broadcasting data that provides a correct time in asynchronous mobile communication terminal are provided. The method of executing a reserved function in a mobile communication terminal includes: when a broadcasting function is executed, performing (1) extracting a time information from received broadcasting data, (2) calculating a time difference between a time of the extracted time information and a corresponding operating time of the mobile communication terminal, and (3) storing the calculated time difference as a time difference information; and if a reservation time for executing a specific function is set and when the operating time reaches the set reservation time based on the stored time difference information, executing the specific function.