Sterilizing method

A method of sterilizing containers by using a peracetic acid-type sterilizing composition solution, wherein the sterilizing composition solution containing peracetic acid, hydrogen peroxide, acetic acid and catalase as prepared in a circulating tank (1) is heated through a heating unit (3), fed to a sterilizing unit (4), and is recovered in the circulating tank (1) after it is used for the sterilization, wherein the catalase is added to the sterilizing composition solution in a circulating passage of after it was used for the sterilization but before it is fed to the heating unit. This makes it possible to suppress the catalase from losing its activity, to maintain the sterilizing power of the sterilizing composition solution, and to use the sterilizing composition solution in a circulating manner without cooling it saving, therefore, the heat energy providing advantage in economy.