The result of dyeing on stretch Nylon by acid dyestuff folloues as; 1) The result of having respectively dyed levelling acid dyes, Erio Fast Red 2G5, and Polar Red RS Conc. of milling acid dyes in neutral dye Lath (pH6.2) showed that in bath low temperature and high temperature the beginning exhaustion of Polar Red RS Conc. of the above two dyestuffs turned out to be excellent and the last exhaustion in dyeing the two dyrestuffs had little difference to each other. In neutral dye bath, the practical dyeing for 40 minutes, increasing the temperature gradually from 7$0^{circ}C$ to 9$0^{circ}C$, had also resulted in excellence. 2) As the result of dyeing in weskly acid bath (pH5.6) Polar Red RS Conc. was good in the beginning exhaustion, and the last dyeing in high temperature had no difference in Erio Fast Red 2GS and Polar Red RS Conc having for 30 minutes from 7$0^{circ}C$ in the practical dyeing, the dyeing for 30 minutes under the gradually increased temperature to 9$0^{circ}C$ was fairly good. 3) In strong acid bath (pH 3.0) the beginning exhaustion in low temperature proved to be pretty good in polar Red RS Conc. and in the last dyeing in high temperature, Erio Fast Red 2GS and Polar Red RS Conc. was equal to math other. 4) According to the result of Fastness, Erio Fast Red 2GS was not so good in water and washing compared with polar Red RS Conc, and it is the apposite in Rubbing Accordingly in practical use a little difference between them does not bring any disturbance.