To reduce the time required to start a drink filling operation or the time interval between productions. In a method of sterilizing a drink filling apparatus that includes drink supply piping that feeds a drink into a filling machine through a heating sterilization part, a heated liquid or heated steam is fed to the drink supply piping, temperatures of the drink supply piping at a plurality of positions are detected at predetermined time intervals, a lowest temperature is selected from the detected temperatures, an F value is calculated for the selected lowest temperature, the calculated F value is integrated, and a sterilization step is ended when the integrated F value reaches a target value.