A method for preparing a magnetic recording medium by forming a ferromagnetic vapor deposition film on a non-magnetic support moving along a rotating drum by an oblique incident evaporation method, in which a vapor flow of ferromagnetic metal is vapor-deposited on the support between a maximum incident angle and a minimum incident angle, while introducing a first oxidizing gas near the place where vapor flow of ferromagnetic metal is introduced at the minimum incident angle, and introducing a second oxidizing gas near the surface of the ferromagnetic vapor deposition film on the support which is moving on the rotating drum, wherein the improvement comprises introducing the first and second oxidizing gases so that .DELTA.p.sub.2 /.DELTA.p.sub.1 is not less than 5, wherein .DELTA.p.sub.1 is the increase of pressure due to the introduction of the first oxidizing gas near the place where the vapor flow of ferromagnetic metal is introduced at the minimum incident angle, and .DELTA.p.sub.2 is the increase of pressure due to the introduction of the second oxidizing gas near the surface of the ferromagnetic film after the vapor deposition.