To provide a lubricant, especially a lubricant for a magnetic recording medium, having excellent lubricating characteristic and sustaining lubricating effects even after long hours use by attaching well to an object to be lubricated.

This lubricant is made of at least one compound selected from compounds expressed by general formula (a), wherein R1 and R2 each represents hydrogen, an aliphatic alkyl group or an aliphatic alkenyl group; a is an integer of 1-12; v is an integer of 1-12; w is an integer of 1-6; z is an integer of 1-5; and h and k each is an integer of 0-30. A lubricant layer of the magnetic recording medium is formed with this lubricant.