A glycolipid methyl ester represented by the formula (I), ##STR1## wherein R.sub.3 represents a hydrogen atom or a methyl group, and R.sub.4 represents a saturated or unsaturated hydrocarbon group having 12 to 16 carbon atoms when R.sub.3 is a hydrogen atom, and R.sub.4 represents a saturated or unsaturated hydrocarbon group having 11 to 15 carbon atoms when R.sub.3 is a methyl group, is produced by adding at least one polyhydric alcohol represented by the formula (III) or (IV), ##STR2## wherein R.sub.5 represents a hydrogen atom or a methyl group, R.sub.6 and R.sub.7 represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and m and n represent integers from 1 to 6, to hydrated Sophorolipid, removing water by distillation under reduced pressure, and subjecting the resulting Sophorolipid-polyhydric alcohol system to methanolysis and methylation by reaction with methanol in the presence of a strong acid.