A microorganism that produces 5-aminolevulinic acid, wherein the microorganism has a 5-aminolevulinic acid dehydratase variant having a reduced inhibitor constant for a 5-aminolevulinic acid dehydratase inhibitor. A microorganism that produces 5-aminolevulinic acid, wherein the microorganism is a photosynthetic bacterium that produces 5-aminolevulinic acid without light irradiation. A process for producing 5-aminolevulinic acid comprising the step of culturing a microorganism that produces 5-aminolevulinic acid in a culture medium under at least one condition selected from the group consisting of (a) less than 1 ppm of dissolved oxygen concentration in the culture medium, (b) from -180 to 50 mV of oxidation-reduction potential in the culture medium, and (c from 5.times.10.sup.-9 to (KrM-2.times.10.sup.-8) (mol of O.sub.2 /ml.multidot.min.cndot.cell) of cellular respiration rate, wherein KrM represents the maximum cellular respiration rate when oxygen is supplied in an excess quantity.