A portable electronic apparatus calibrates a geomagnetism sensor at a suitable timing. When a key is operated in a power-saving mode, the power-saving mode ends, and a detection value of a geomagnetism sensor is calibrated. The calibration is executed in a state where a user tries to view a screen of a display part, therefore the calibration is executed in a state where an angle of housings with respect to the horizontal plane is suitable, and a calculation precision of a bearing is improved. By executing calibration during activation of the navigation application useless calibration is not carried out, and an increase of power consumed is suppressed.