The adsorption of enantiomers and a racemic mixture of tyrosine (tyr) on Cu(111) has been investigated by cyclic voltammetry and electrochemical scanning tunneling microscopy. D-tyr and L-tyr molecules adsorb on Cu(111) and show a (4 x 4) structure. The mirror symmetry between two adlayers is demonstrated by high-resolution scanning tunneling microscope images. The spontaneous separation of racemate into homochiral domains is observed. The result presented here is hoped to supply direct evidence for the chiral adlayer ordering at the solid/liquid interface.