PURPOSE: To prepare optically active methionine amide in which ee(enantiomer excess) of the obtained methionine amide is not decreased and methionine amide/ mandelate has good filtrating property and processability.

CONSTITUTION: A process is for preparing optically active methionine amide in which a mixture of D- and L-methionine amide or the Schiff bases thereof is at least partly converted, optionally in the presence of 0.5-4 equivalents of aldehyde, relative to the amount of methionine amide and water, in the presence of an org. solvent, by using less than 1.2 equivalents of L- or D-mandelic acid, respectively, relative to the amount of D- or L-methionine amide, respectively, or the Schiff bases thereof, present in the mixture of D- or L-methionine amide or the Schiff bases thereof, into a salt of methionine amide and mandelic acid, is separated from the reaction mixture in which a portion consisting substantially of one of the diastereoisomers of the salt is obtained and the salt is converted into the optically active methionine.