A magnetic disk comprising a non-magnetic support having provided thereon a magnetic layer comprising ferromagnetic particles, and a binder resin, wherein said magnetic layer is such that when sputtering is conducted on said magnetic layer from the surface of the magnetic layer in the direction of the depth of the magnetic layer by the Auger electron spectroscopic method, and the concentration of carbon atoms resulting from the sputtering is measured, a sputtering time (T.sub.1) required for the carbon atom concentration to be (C.sub.0 +C.sub.2)/2 is in the range of from 8 to 98 minutes, wherein C.sub.0 is a carbon atom concentration value obtained at the initiation of the sputtering and C.sub.2 is a carbon atom concentration value after the carbon atom concentration becomes constant.