Embodiments of the invention provide a magnetic disk device which lowers the cost, maintains reliability by compensating the thermal dent or protuberance caused by a change in the environmental temperature, makes it possible to increase the recording density by decreasing the floating amount of the slider, to increase the capacity of the device or to decrease the size thereof. In one embodiment, a magnetic disk device comprises a magnetic disk, a magnetic head slider, and a drive unit for moving the magnetic head slider, wherein an air stream is generated between the magnetic disk that rotates and the magnetic head slider to effect the recording or the reproduction in a state where the magnetic head slider is floating. The magnetic head slider includes a slider substrate portion and a thin-film head portion that has recording and reproducing elements, a metal film, and an insulating film formed on the slider substrate portion and constituting a slider-floating plane along with the slider substrate portion. The slider substrate portion includes a silicon substrate with a recessed portion, and a metal member buried in the recessed portion.