A method for producing L-phenylalanine by fermentation which comprises aerobically culturing an L-phenylalanine-producing microorganism in an aqueous culture medium and recovering the L-phenylalanine accumulated in the culture medium, the L-phenylalanine-producing microorganism having been constructed by incorporating a recombinant plasmid DNA, into which a DNA fragment controlling resistance to a phenylalanine antagoinst, obtained from a chromosomal DNA of a mutant of the genus Bacillus resistant to the phenylalanine antagonist, has been inserted, into a recipient strain of the genus Bacillus.