When a camera server receives an instruction involving invalidation of viewing limitation (masking processing) of video from a privileged client, the camera server limits viewing of video data with respect to a general client and a recording client. The camera server stores the video data of a limited period in a secondary storage device. When the camera server receives an instruction involving validation of the viewing limitation from the privileged client, the camera server transmits the stored video data of the limiting period to the recording client.