A camera device generates a captured image, extracts flow line information relating to a staying position or a passing position of a moving object, and transmits the generated captured image and the extracted flow line information of the moving object to a server device for each predetermined transmission period. The server device generates a flow line analysis image in which the flow line information of the moving object is superimposed on the captured image and displays the generated flow line analysis image on a displayer. Furthermore, the server device switches a first flow line analysis image in a first predetermined period to a second flow line analysis image in a second predetermined period according to an operation of changing the period, and displays the resulting flow line analysis image.