PURPOSE: To obtain serine, a kind of amino acid, by reacting monochloroacetic acid with ammonia and formaldehyde in the pressure of a metal compound capable of forming a glycine metal complex.

CONSTITUTION: Monochloroacetic acid is reacted with ammonia and formaldehyde in the presence of a metal compound (e.g., copper ion, nickel ion, zinc ion, cadmium ion capable of forming a glycine metal complex in a solvent such as water, methanol, etc. at 30W200°C for 0.5W5hr preferably in an oxidative atmosphere in the coexistence of a base such as a caustic alkali, pyridine, etc. to give the desired substance. The ion is prepared by adding a copper salt, nickel salt, zinc salt, cadmium salt or a hydroxide of the metal to the reaction solution. An amount of ammonia used is ≥an equimolar amount, preferably 2W10mol based on 1mol monochloroacetic acid.