To provide a method of measuring a surface lubricant of magnetic disk medium utilizing such a measurement method that makes the contact state with a magnetic head observable and measurable even in a flexible magnetic disk medium, and to make a highly durable magnetic disk medium obtainable.

Dummy heads 4 and 5 formed of a transparent material to the same shape as the shape of the magnetic head of a semi-floating type are brought into contact with both surfaces of the magnetic disk medium 1 which is rotated at a prescribed number of revolutions and has flexibility and the amounts of the lubricant sticking to the dummy heads 4 and 5 are measured by every prescribed time. The magnetic disk medium having the characteristic that the amounts of the lubricant sticking to the heads after one hour of traveling is 10 to 200% of the amounts of the lubricants sticking thereto after 10 minutes of traveling is provided with good durability.