A magnetic disk device, which is provided with a magnetic head slider
mounted with a magnetic head and a magnetic disk, and of which the
magnetic head slider has the possibility of contacting the magnetic disk
at the vicinity of the magnetic head. The magnetic head slider has the
size of 1.25 mm or less in length, 1 mm or less in width and 0.3 mm or
less in thickness, and the friction force exerted between the magnetic
head slider and the magnetic disk is 10 mN or less. The magnetic head
comprises four substantially parallel surfaces and the depth from a first
surface which is the most adjacent surface to the magnetic disk to a
second surface is 10 nm to 50 nm, the depth from the second surface to a
third surface is 50 nm to 200 nm, and the depth from the third surface to
a fourth surface is 400 nm to 1 .mu.m.
