The present invention provides: a process for producing an amino acid which comprises adding crystals of the amino acid having an average particle size of 1 to 120 μm to a medium so that the concentration of the crystals of the amino acid becomes 0.5 g/l or more, culturing a microorganism having the ability to produce the amino acid in the medium, allowing crystals of the amino acid to form and accumulate in the medium, and recovering the crystals of the amino acid from the culture; and a process for producing an amino acid which comprises adding crystals of the amino acid to a medium so that the total surface area of the crystals of the amino acid in the medium becomes 0.02 m2/l, culturing a microorganism having the ability to produce the amino acid in the medium, allowing crystals of the amino acid to form and accumulate in the medium, and recovering the crystals of the amino acid from the culture.