Magnetic north detecting device and magnetic north detecting method

The magnetic north detecting device comprises: a 3-dimensional geomagnetism sensor unit including three geomagnetism sensors for detecting respective components of a geomagnetic field intensity in respective directions of three perpendicular coordinate axes; and a 3-dimensional operation functional section for carrying out an operation on the basis of the components of the geomagnetic field intensity detected by the geomagnetism sensors, and calculating a magnetic north direction of the geomagnetism, and the 3-dimensional operation functional section carries out the operation and calculates the magnetic north direction of the geomagnetism, based on two assumptions that: (i) at least one axis of three coordinate axes of the 3-dimensional geomagnetism sensor unit is level to the earth surface; and (ii) an angle of a geomagnetic field vector which is calculated from the detected components of the geomagnetic field intensity, referring to the earth surface, coincides with a dip angle of the geomagnetism which is assumed beforehand.