A positioning device includes a first storage device having stored therein received signal strength data in time series according to mobile device data, a second storage device having stored therein relative movement data of the mobile device in time series within a relative coordinate system, and a processor configured to calculate a first neighboring time at which the mobile device becomes closest to a first base station in the plurality of base stations based on the received signal strength data and a second neighboring time at which the mobile device becomes closest to a second base station of the plurality of base stations, and convert the relative movement data in the second storage device into position coordinates data specifying an absolute position of the mobile device in an absolute coordinate system using the first base station as a reference point from the first neighboring time to the second neighboring time.