Provided are: a method of removing 2-chloro-1,3,3,3-tetrafluoropropene (1224xe), the method including bringing a mixture containing 1224xe and 1224yd into contact with an alkali optionally in the presence of a phase transfer catalyst; and a method of producing 1-chloro-2,3,3,3-tetrafluoropropene (1224yd), the method including bringing a mixture containing 1224xe and 1224yd into contact with an alkali optionally in the presence of a phase transfer catalyst.