A magnetic recording medium is provided that can ensure stable recording and reproducing characteristics with little off-track even when a track density in the direction of width of the tape is very high and 50 lines / mm or more, an off-track margin is 5 μm or smaller, and a variation that is permitted at maximum as a dimensional variation in the direction of width of the tape itself due to environmental factors such as the change of temperature and humidity, the change of tension, a creep, etc. is small as low as 0.10% or less. Assuming that Young's modulus in the direction of width of a non-magnetic substrate is X and Young's modulus in the direction of width of the back layer is Y, X is 850 kg / mm2 or more, or when X is less than 850 kg / mm2, X×Y is 6×105 or more, and assuming that Young's modulus in the direction of width of a layer including a magnetic layer is Z, Y / Z is not larger than 6.0.