PURPOSE: To diagnose surely the degree of applicability to permanent wave by giving a specified tension to a hair to be inspected, contacting it with a specified reagent and measuring the elongation of the hair in relation to time.

CONSTITUTION: An appropriate number of inspected hairs 1 are inserted into an inserting hole 2 formed in a capillary tube 3 of a specified length and one end of the hairs 1 is fixed to one end of the capillary tube 3. The capillary tube 3 is held vertically by clamping its several positions with clamp holders 6, the hairs 1 are sticked and fixed to a fixer 8 at a position a specified dimension p apart from the end 7 of the capillary tube 3 and a tension is given to the hairs with a wieght 9 of a specified weight. If a reagent is dropped to the hairs 1 next, they begin to elongate after a while. From a time until the start of the elongation of the hairs 1 or a time by the time when they reach a specified length, whether the hairs are healthy and strong or they are injured and weak is judged. As it is difficult to apply permanent wave to hair which is hard to manage and easy to apply it to soft hair, hair can be diagnosed correctly by said method.