To provide a hair iron for a straight permanent wave which never brings differences to effects of ironing, gives no pain in a head part, prevents hairs from coming off or being cut, and gives a straight permanent wave with an excellent finish without depending on a skilled person.

The hair iron for a straight permanent wave is equipped with tightly holding parts for hairs which are formed to come close/be separated with the closing/opening of arm bodies and are located at the end parts of a pair of arm bodies pivotally attached to open and close. A rotatable roller is attached to at least one of the tightly holding parts for hairs, and the rotating axis is located in a direction where the arm body extends.