We have investigated the morphology of a micelle consisting of a calix[4]arene-derivative surfactant under various NaCl concentrations CS by small-angle X-ray scattering (SAXS) and estimated the molar mass dispersity index (D) over tilde of the micelles by field flow fractionation (FFF). We found the sphere-to-cylinder morphology transition induced by increasing C-S. Although (D) over tilde was very low in the spherical morphology, (D) over tilde increased when the morphology became cylindrical.