A track estimating device comprising: a signal observing unit configured to receive a plurality of signals, each signal being outputted from a corresponding signal source; a position estimating unit configured to estimate, for each signal source, a respective observation position associated with each signal source from a strength of the signal received by the signal observing unit, each observation position being an estimate of a position of an observation target on which the signal observing unit is mounted; a data association hypothesis generating unit configured to generate a plurality of data association hypotheses, each of the data association hypotheses including a hypothesis and an observation position estimated by the position estimating unit, each hypothesis including a track of the observation target; a reliability calculating unit configured to calculate a reliability of each observation position, using a probability density distribution of the associated signal strength at the observation position estimated by the position estimating unit; and a track determining unit configured to select one data association hypothesis from the plurality of data association hypotheses generated by the data association hypothesis generating unit, by referring to the reliability of the corresponding observation position calculated by the reliability calculating unit, and to determine a track included in the hypothesis included in the selected data association hypothesis to be a track of the observation target, wherein the track determining unit includes a track updating unit (25;72) configured to update the track included in the hypothesis included in each corresponding data association hypothesis, using at least the observation position included in the corresponding data association hypothesis, the corresponding data association hypothesis being one of the data association hypotheses generated by the data association hypothesis generating unit. a signal observing unit configured to receive a plurality of signals, each signal being outputted from a corresponding signal source; a position estimating unit configured to estimate, for each signal source, a respective observation position associated with each signal source from a strength of the signal received by the signal observing unit, each observation position being an estimate of a position of an observation target on which the signal observing unit is mounted; a data association hypothesis generating unit configured to generate a plurality of data association hypotheses, each of the data association hypotheses including a hypothesis and an observation position estimated by the position estimating unit, each hypothesis including a track of the observation target; a reliability calculating unit configured to calculate a reliability of each observation position, using a probability density distribution of the associated signal strength at the observation position estimated by the position estimating unit; and a track determining unit configured to select one data association hypothesis from the plurality of data association hypotheses generated by the data association hypothesis generating unit, by referring to the reliability of the corresponding observation position calculated by the reliability calculating unit, and to determine a track included in the hypothesis included in the selected data association hypothesis to be a track of the observation target, wherein the track determining unit includes a track updating unit (25;72) configured to update the track included in the hypothesis included in each corresponding data association hypothesis, using at least the observation position included in the corresponding data association hypothesis, the corresponding data association hypothesis being one of the data association hypotheses generated by the data association hypothesis generating unit.