The method of trivalent chromium plating has been studied. The relations between the mixing ratio of chromic chloride and DMF, and the corrosion resistance and throwing power of plated chromium have been investigated. As a result, the best result has been obtained, when the mole ratio of chromic chloride and DMF are 0.8 and 5.4M respectively, and it has been learned that the amounts of DMF added have particularly the delicate effects in chromium plating procedures. The results of measuring of pH and reduction potentials of chromium plating bath with addition of DMF showed that the functions of DMF have both the buffer actions for the solution and the complex formation of trivalent chromium.