A magnetic recorder for performing at least one of magnetic recording and magnetic reproduction on a running magnetic tape, comprising: a magnetic head mounted so as to slidably abut on the magnetic tape; a subject portion made of the same material as that of the magnetic head and provided so as to slidably abut on the magnetic tape; a tinge detection sensor for detecting a color of a surface of the subject portion slidably abutting on the magnetic tape; and a judgment portion for acquiring a detection signal output from the tinge detection sensor when the color of the surface of the subject portion detected by the tinge detection sensor changes to a specific color.