It is possible to rapidly or highly accurately estimate a highly reliable offset according to situations and improve further the reliability of the estimated offset even if a measurement data is not obtained in a space in which the magnitude of a vector physical quantity to be measured is uniform. The offset included in the obtained vector physical quantity data are statistically estimated based on a predetermined evaluation formula using difference vectors. In the estimation of the offset, reliability information on a reference point is calculated based on at least one of the vector physical quantity data, the difference vectors and a plurality of estimated reference points according to a calculation parameter for calculating the reliability information on the reference point, whether or not the reference point is reliable is determined by comparing the reliability information with a determination threshold value.