To provide a safe V-shaped hair iron that can be used safely without damaging hair even by a less-experienced user when waving, straightening or curling hair at a low cost.

This V-shaped hair iron has thermal plates on one or two sides of the insides of the tip of the case of a V-shaped grip and is used for waving, straightening or curling hair while electrically heating the thermal plates and pinching the hair with the thermal plates. The hair iron is structured by connecting a control device with a temperature monitoring function to keep the temperature constant by setting in a stepless manner the temperature during use, and incorporating a regulating means to automatically regulate the angle of the thermal plates in parallel with the thermal plates provided one or two sides of the tip of the V-shaped grip case.