In an MR element constituted in such a manner that a pinned layer whose magnetization direction is fixed, a nonmagnetic spacer layer, and a free layer whose magnetization direction is changed according to an external magnetic field, are laminated in this order; the free layer has a multilayer constitution including a magnetic body mixed with an element having 4f electrons at a certain ratio. Specifically, the first layer in contact with the spacer layer, the third layer, the fifth layer, and the seventh layer of the free layer are formed by mixing Nd, Sm, Gd, or Tb into CoFe. The second layer and the sixth layer of the free layer are formed by mixing Nd, Sm, Gd, or Tb into NiFe. The third layer of the free layer is Cu. A damping constant of the free layer is greater than 0.018.