PURPOSE: To obtain a binder which can form a magnetic recording medium having excellent wear resistance, mechanical characteristics and electrical characteristics when irradiated with radiations by bringing isocyanate ethyl methacrylate into reaction with a prepolymer having OH groups.

CONSTITUTION: The magnetic layer constituted by binding magnetic powder with the polymer obtd. by bringing a copolymer of vinyl chloride and vinyl alcohol or the like having ≥2 OH groups in one molecules as the prepolymer and the isocyanate ethyl methacrylate into reaction as a binder is formed on a base. The magnetic paint formed by dissolving such binder into cyclohexane and toluene, etc. to prepare a soln. and dispersing the magnetic powder into such soln. is coated on the base and dried; thereafter electron rays, etc. are irradiated to the coating to cure the same. The binder which has good adhesiveness to the base, the excellent wear resistance and electromagnetic conversion characteristic, decreases output fluctuation and permits the manufacture of a magnetic tape, etc. having a goo S/N ratio is thus obtd.