To provide a method for humidifying hair and reducing damage for readily improving humidification of hair and damage of hair using both positive ions and negative ions.

In the method, a positive ion generation means 10b for discharging electricity between electrodes by applying voltage and generating positive ions coupled with water molecules, and a negative ion generation means 10a for discharging electricity between electrodes by applying voltage and generating positive ions coupled with water molecules are prepared, and the positive ions and negative ions respectively generated by the positive ion generation means 10b and the negative ion generation means 10a are applied to hair for humidifying the hair and reducing damage of the hair.