Abstract: A method of producing coryneform bacteria having improved amino acid or nucleic acid productivity comprising the steps of introducing a mutation in a promoter sequence of amino acid- or nucleic acid-biosynthesizing genes on a chromosome of a coryneform bacterium to make it close to a consensus sequence, or introducing a change in a promoter sequence of amino acid- or nucleic acid-biosynthesizing genes on a chromosome of a coryneform bacterium by gene recombination to make it close to a consensus sequence, to obtain mutants of the coryneform amino acid- or nucleic acid-producing microorganism, culturing the mutants and selecting a mutant capable of producing the intended amino acid or nucleic acid in a large amount. This method allows the construction of a mutant capable of enriching or controlling the expression of an intended gene without using a plasmid and to promote production of amino acids in a high yield by recombination or mutation.