A recording format comprising, in order to improve the adjustement efficiency of a high density recording/reproducing device by automatic adjustement and to realize excellent compatible reproducing characteristics despite the characteristics variation of the magnetic head, change of characteristics due to wear and characteristics variation of the recording medium, two recording areas of the single repetitive data of a reference wavelength for the adjustment of a reproducing amplifier and a short wavelength for the adjustment of a reproducing equalizer, a recording area of adjustment data for the error detection and the precise adjustment of the reproducing equalizer, one or more no-data areas for the recording system adjustment, identification data which indicate that the medium is for the automatic adjustment and indicate the types of the areas depending on the kind and necessity, and, if necessary, time codes; a recording device which recordes the recording format in recording medium; and an automatic adjustment device which performs automatic adjustment by using the data of the recording format on the reference recording medium.