information acquiring means for acquiring location information pieces and error information pieces of a mobile object measured at present and at a plurality of time points in the past; and

arithmetic processing means for arithmetically processing the location information pieces and the error information pieces acquired by the information acquiring means, for estimating a moving area per unit time of the mobile object from the location information pieces and the error information pieces of the mobile object measured at a plurality of time points in the past, acquired by the information acquiring means, for estimating an existing area at present of the mobile object from the moving area per unit time of the mobile object and from the location information piece and the error information piece of the mobile object measured at a time point in the past, acquired by the information acquiring means, and for estimating a location at present of the mobile object from the existing area at present of the mobile object and from the location information piece and the error information piece of the mobile object measured at the present time, acquired by the information acquiring means.