PURPOSE: To provide a lubricant which is excellent in lubricity and less susceptible to dissipation when incorporated in a binder-contg. coating layer of a magnetic recording medium and exhibits a lubricating action for a long period of time, which comprises a polyfunctional org. isocyanate compd. and, bonded thereto, a particular fluorinated org. group.

CONSTITUTION: A lubricant comprising as an active ingredient a lubricating compd. composed of a polyfunctional org. isocyanate compd. and, bonded thereto, an org. group. having a terminal perfluoroalkyl group through a urethane bond {e.g., a compd. of formula I [wherein X is a divalent or trivalent org. group comprising a residual group of a polyfunctional org. isocyanate compd.; R is a 2C or higher (substd.) alkylene; Rf is a 4W20C perfluoroalkyl; n is 1W21; and l is 2 or 3]}. Examples of the lubricating compd. include a compd. of formula II. These compd. is excellent in lubricity and less susceptible to dissipation when incorporated in a binder-contg. coating layer, such as a magnetic layer or a backcoat layer, of a magnetic recording medium and exhibits a lubricating action for a long period of time, so that it is possible to improve the durability of the magnetic recording medium.