PURPOSE: To provide a fiber structure free from change with the passage of time and excellent in durability by treating the fiber structure in a space between electrodes without bringing the fiber structure into contact with the electrodes in an atmosphere of low-temperature plasma of tetrafluoromethane generated between these electrodes.

CONSTITUTION: A fiber structure consisting of a synthetic fiber, semisynthetic fiber, natural fiber, etc., is treated in a space between electrodes without bringing the fiber structure into contact with the electrodes in an atmosphere of low temperature plasma of tetrafluoromethane generated between these electrodes. Then the treated fiber structure is allowed to stand in an usual chamber from several ten minutes to twenty several hours to change the fiber surface into hydrophilic. The resultant fiber product has excellent durability and is free from the change with time and exhibits highly hydrophilic property.