A method for removing the fluorine component from waste water which is produced during the manufacturing process of highly reactive polybutene and contains high concentration of fluorine component, is disclosed. The method comprises a step of adding to the waste water a treating agent selected from a group of Al compound, Ca compound and mixture thereof at temperature of 50 to 300° C. for reaction, whereby boron trifluoride neutralized salt is decomposed to form Al salt or Ca salt of fluorine component so that the fluorine component is removed in the form of the Al salt or the Ca salt of fluorine component.