The critical concentrations of ${alpha}$-amino capric acid for micelle formation have been determined by the surface tension measurements in both acidic and alkaline solutions, and also by the dye titration using Rhodamine B in alkaline solutions. The critical micelle concentrations obtained by the two methods show the good agreements within experimental errors. Since ${alpha}$-amino acid is an ampholyte, it may aggregate to form the micelles in both more acidic and basic media than its isoelectric point. It is found that the basic media are rather preferable for the micelle formation than the acidic media. The effect of gegen ions upon the critical concentration for micelle formation in alkaline media is similar to that expected from the salt effect on the CMC (Critical Micelle Concentration).