Abstract: This invention is directed to a lubricant for treating synthetic fibers characterized by adding a polyethylenepolyaminepolyacetic acid derivative of the following formula (I) to a composition comprising so far known lubricating agent and surfactant, and imparts lubricating property and antistatic property to synthetic fibers in the production and processing steps thereof: ##STR1## wherein R.sub.1 and R.sub.2 is hydrogen or an alkyl or alkenyl group of 1-22 carbon atoms; n is an integer of 0-4; and M.sub.1.sup.+ -M.sub.5.sup.+ are respectively selected from the group consisting of hydrogen ion, alkali metal ion, and ammonium ion expressed e.g. by the following formula (II): ##STR2## wherein R.sub.3, R.sub.4 and R.sub.5 are respectively selected from the group consisting of hydrogen, alkyl, alkenyl, hydroxyalkyl, polyethoxyalkyl, polypropyleneoxyalkyl and polyethylenepolyaminoethyl.