When a moving area and a fixed area are detected on a screen, it is determined whether the detected moving area and the fixed area overlap or not. As a result, when it is determined that an overlap exists, a compound area is set so as to include noticed areas to be overlapped. Next, the set compound area is compressed by taking advantage of an ROI function so as to keep a compression target size of the whole screen. Therefore, this enables to reduce a processing amount of a JPEG 2000 CODEC. In addition, a size and a location of the ROI area are changed so as to include a motion range of the object with movement into the noticed area. As a result, it is capable to progress in a surveillance function, because the motion range of the object with movement is included into the noticed area.