The present invention provides a technique for enhancing the added value of flow line information. The flow line combining device is provided with: an acquisition unit for acquiring first flow line information indicating a trail of positions determined by using a first method and second flow line information indicating a trail of positions determined by using a second method which is different from the first method; a determination unit for assessing overlap in the trails respectively indicated by the acquired first flow line information and the second flow line information; and a combining unit for generating third flow line information which combines the first flow line information and second flow line information if the trail overlap assessed by the determination unit meets a predetermined condition.