To simplify management of a sterilization process of a filling nozzle, a method for sterilizing a filling nozzle is provided. In the method for sterilizing a filling nozzle, hot water or a liquid chemical agent is fed to drink supply piping that feeds a drink to a plurality of filling nozzles at the same time, the hot water or liquid chemical agent is discharged from all the filling nozzles, a flow rate of the hot water or liquid chemical agent is detected at all the filling nozzles, a representative temperature of the hot water or liquid chemical agent upstream or downstream of at least one filling nozzle is measured, and the sterilization process is ended when both the flow rate at each filling nozzle and the representative temperature reach respective target values.