Disclosed is a small-sized two-axis magnetic field sensor having a function to cause a magnetic field canceling an external offset magnetic field. The two-axis magnetic field sensor contains a plane coil disposed on a plane and four sets of magneto-resistance element pairs on a plane parallel to the plane coil. The plane coil includes at least two pairs of parallel conductors, and two magneto-resistance elements cross only a single conductor of the coil. A current for canceling the external offset magnetic field is determined in advance, and while a DC current that causes total magnetic fields of biasing magnetic fields plus a magnetic field for canceling the external offset magnetic field flows through the coil, intermediate potential outputs from the magneto-resistance element pairs are detected to measure a magnetic field direction, such as geo-magnetism.