PURPOSE: To prevent adsorption and to lessen an increase in friction force by a contact start-stop by specifying the roughness on the surface of the magnetic disk and the film pressure of a lubricant to values of respective specific ranges.

CONSTITUTION: The magnetic head 2 is held pressed onto a magnetic disk 1 by a suspension 3 when a magnetic disk device is not used. The roughness of the surface of the magnetic disk 1 of such magnetic disk device of a contact start-stop(CSS) system is specified to the range of Rp=17 to 37mm and the thickness of the lubricant to t=3 to 7mm. Both the friction force and adsorption force are increased in the region where the Rp is smaller than the above- mentioned range. Conversely, the low floating of the magnetic head 2 is not possible in the region where the Rp is large. The lubricant film is removed by the CSS in the region where the thickness of the lubricant film is thin. The adsorption power increases in the region where the lubricant film is thick.