PURPOSE: To improve the vertical orientation performance and the recording density of a magnetic disk without receiving the surface effect of an aluminum alloy substrate, by plating Ni-P on said alloy substrate to form a vertically magnetized film on the plate layer.

CONSTITUTION: A nonmagnetic Ni-P layer 2 is formed with about 30μ thickness on an aluminum alloy substrate 1 by an electroless plating process. A thin film 3 of Co-Cr, etc. is sputtered on the layer 2 to obtain a vertically orientated/magnetized film, or the film 3 is formed after a soft magnetic film 6 of "Permalloy", etc. is formed on the layer 2. The vertical orientation performance of the film 3 is improved since the layer 2 receives no surface effect of the substrate 1. Furthermore the film 3 has a heat expansion coefficient close to that of the substrate 1 and therefore produces neither exfoliation nor else. This example eliminates the use of Al of high purity and a Ti layer which are needed for a conventional anodized aluminum substrate. This attains the low cost and improvement of recording characteristics of high density.