PURPOSE: To provide the subject apparatus containing a heater unit, a reaction chamber, a weighing unit, a liquid feeder and a controller as its constituting components and capable of automatically and readily producing various kinds of amino acid derivatives.

CONSTITUTION: An amino acid solution is fed from a liquid feeder 1 to a reaction chamber 2 and its solvent is evaporated by nitrogen gas 4 while simultaneously heated by a heater unit 3. A buffer solution 5 for a reaction and a reagent 6 for derivatization respectively stored at a low temperature in a refrigerator unit 7 are weighed by a weighing unit 8 and sent to the reaction chamber 2 in order. The reaction chamber 2 is then heated by the heater unit 3 to a temperature required for a derivatization reaction. After a prescribed reaction time, heating is discontinued and a required amount of a buffer solution 9 for dilution is fed through the liquid feeder 1 so as to adjust pH of the amino acid solution after completion of the derivatization reaction to a value within a range suitable for amino acid analysis. All of timing for feeding the liquid, weighing, switching of flow path, etc., are controlled by a controller 10.