To provide a V-shaped hair iron, used with a little experience and with security without damaging user's hair in waving, straightening or curling his/her hair.

This hair iron has plate-like heating plates on both sides inside of the tips of cases of a V-shaped grip, and the heating plates are heated by electricity to straighten user's hair while being held. At least one of the heating plates provided inside the tips of the cases of the V-shaped grip is provided with a built-in adjusting means for automatically adjusting the angle thereof, whereby in holding his hair between the heating plates to be straightened, both flat plate-like heating plates are made parallel to each other.