To roll up the hair by extracting an application tool on which an end part of the hair is hooked from the inside of a flat hollow part of a hair curler, to simplify hair set work, to reduce a time, to reduce a time for heating and drying the hair set on the hair curler, and to reduce heat damage of the hair.

The hair curler is made of synthetic resin, which is provided with many holes where the longitudinal orthogonal direction communicates with a space part inside in prescribed width on the right and the reverse sides, is cylindrically rolled in a helical shape, is formed into a flat straight shape so as to be elastically deformable, and has a high heat conductivity medium.