The present invention provides a thin film head having a magnetoresistance effect element which includes at least two magnetic films, a nonmagnetic film sandwiched between the magnetic films, and leads connected to the magnetoresistance effect element wherein the width of one of the magnetic films, which essentially responds to a signal magnetic field, is not more than a distance between leads. The present invention provides a thin film head having a magnetoresistance effect element which includes at least two magnetic films and a nonmagnetic film sandwiched between the magnetic films, which makes use of a change in magnetic resistance caused by spin-dependent scattering, wherein at least a portion of one magnetic films, which essentially respond to a signal magnetic field extends in a direction same as that of the signal magnetic field.