A person is detected from a moving image of the monitoring area, and position information on the person is acquired. Temporal statistical processing is performed on the position information, statistical information relating to a staying situation of the person is acquired in accordance with setting of a target period of time for the statistical processing, and thus a heat map moving image is generated. Furthermore, a mask image corresponding to a person image area is generated at every predetermined point in time based on the position information on the person. A monitoring moving image that results from superimposing the heat map image and the mask image onto a background image is generated and is output at every predetermined point in time.