A magnetoresistive device comprising a magnetoresistive unit, an upper shield layer and a lower shield shield layer stacked such that the magnetoresistive unit is held between them. The magnetoresistive unit comprises a nonmagnetic metal intermediate layer, a first ferromagnetic layer and a second ferromagnetic layer stacked with the nonmagnetic metal intermediate layer in the middle. When no bias magnetic field is applied, the first and second ferromagnetic layers have mutually antiparallel magnetizations. The magnetoresistive unit further comprises first and second side shield layers, and first and second biasing layers located to be magnetically coupled to the first and second side shield layers, wherein magnetic fluxes fed from the bias magnetic fields pass through the first and second side shield layers positioned in proximity to the magnetoresistive unit such that the magnetizations of the first and second ferromagnetic layers become substantially orthogonal to each other.