A selection circuit selects, as anchors, at least two of a plurality of radio electronic devices and updates the selected anchors based on first information and second information, the anchors being used for position estimation for a mobile terminal, the first information being related to an arrangement of the radio electronic devices, the second information being related to a first position resulting from estimation of a position of the mobile terminal, using the selected anchors. A estimation circuit estimates the first position of the mobile terminal based on third information related to radio communication quality between the selected anchors and the mobile terminal and on the first information related to the selected anchors, and estimates a second position of the mobile terminal based on fourth information related to radio communication quality between the updated anchors and the mobile terminal and on the first information related to the updated anchors.