As shown in FIG. 1, a hairstyle design system comprises an image-processing device 1, an input/output device 2, a graphic system 3, a display device 4, a head-development drawing information-storage device 5, and a hairstyle-design information-storage device 6. In other words, the beautician or the customer designs a desired hairstyle while looking at the display device 4. Information on the designed hairstyle is stored in the head-development drawing information-storage device 5 as numerals and/or symbols assigned to each of a plurality of divided sections. When processing hair, the beautician displays a head-development drawing on the display device 4, and by referring to the drawing the beautician cuts or applies permanent wave to the hair in order to design a hairstyle precisely as desired by the customer and reproduce a predetermined hairstyle accurately.