A magnetic head slider mounted on a magnetic disk unit for supporting a magnetic head that writes and reads information to and from a magnetic disk is constructed such that a depth s1 from the surfaces of leading and trailing pads, which come into contact with a medium surface when the disk is at rest, to stepped surfaces formed on the air inflow side of the leading pads, a depth s2 from the contact surfaces to stepped surfaces formed on the air inflow side of the trailing pad and a step depth s3 from the contact surfaces to the surfaces of side rails are in a relation of s1s2s3. With this arrangement, the slider can follow the waved medium surface at a low flying height with a small flying height fluctuation, thus realizing high density recording, high reliability and reduced cost of the magnetic disk unit.