To provide an MR element which is of high sensitivity and whose reluctivity is high.

This one-dimensional magnetoresistance effect element has a structure in which a plurality of magnetic dot bodies 30 composed of magnetoresistance effect elements are coupled one-dimensionally by a coupling body 40 composed of a nonmagnetic conductive material (e.g. an aluminum material). The respective magnetic dot bodies 30 are arranged in such a way that, when an external magnetic field is zero, their magnetization is not arranged in parallel due to the magnetic interaction between the magnetic dot bodies. When an external magnetic field at a certain value or higher is applied, the magnetization of the magnetic dot bodies 30 is made uniformly in parallel. The external magnetic field which is required to invert their magnetization is at about several hundred Oe in the case of the slender magnetic dot bodies in a length of about several hundred nm, and it is at about several tens of Oe in the case of the magnetic dot bodies having a length of several tens of nm. In addition, when the magnetic dot bodies to be inverted are formed in a disk shape having a diameter of about 50 nm or lower, the magnetic dot bodies can be inverted by a much smaller external magnetic field because their coercive force is small.