1. A target tracking device comprising: a track calculation unit configured to calculate a track of a target based on angular measurement of the target measured by a passive sensor; and a correction unit configured to send correction data to the track calculation unit, wherein the correction unit calculates the correction data based on a state vector of the target input from an external device, and the track calculation unit calculates track for each of a plurality of motion models based on the angular measurement and the correction data, and calculates the track of the target based on the track for each of the motion models, and calculates the track of the target by weighted sum of all tracks for the motion models.