Abstract: A method for slitting a continuously running magnetic tape having a magnetic layer formed on the surface of a non-magnetic substance without producing burring. The tape is slit from the front and rear side surfaces of the magnetic tape by a pair of upper and lower rotary blades having rotational axes substantially parallel to the tape surface and extending in the tape width direction and radially overlapping each other. A gap is formed between blade edges of the rotary blades in the tape width direction having a width in a range of 3% to 20% of the thickness of the magnetic tape.