A video flow analyzing method and a related camera device are applied to determine whether an object passes through a monitoring area. The video flow analyzing method includes drawing two boundaries on a video image correlative to the monitoring area to form a counting path, utilizing endpoints of the two boundaries to define an inlet and an outlet of the counting path, setting an initial point while the object moves into the counting path by crossing one of the boundaries, the inlet and the outlet, setting a final point while the object moves out of the counting path by crossing one of the boundaries, the inlet and the outlet, and utilizing the initial point and the final point to determine whether the object passes through the counting path.