The present invention relates to mutant microorganisms having improved productivity of branched-chain amino acids, and a method for producing branched-chain amino acids using the mutant microorganisms. More specifically, relates to mutant microorganisms having improved productivity of L-valine, which are produced by attenuating or deleting a gene encoding an enzyme involved in L-isoleucine biosynthesis, a gene encoding an enzyme involved in L-leucine, and a gene encoding an enzyme involved in D-pantothenic acid biosynthesis, and mutating a gene encoding an enzyme involved in L-valine biosynthesis, such that the expression thereof is increased, as well as a method for producing L-valine using the mutant microorganisms. The inventive mutant microorganisms produced by site- specific mutagenesis and metabolic pathway engineering can produce branched-chain amino acids, particularly L-valine, with high efficiency, and thus will be useful as industrial microorganisms for producing L-valine.