The present invention relates to an imaging data server. The imaging data server acquires a plurality of types of imaging data pertaining to a plurality of objects of surveillance and transmits the acquired imaging data to a monitoring station over a network. The imaging data server comprises determination section for determining whether or not a change has arisen in the status of each of the objects of surveillance pertaining to a plurality of types of the imaging data; and a priority transmission section for transmitting, to the monitoring station, imaging data pertaining to an object of surveillance in which the status change is determined to have arisen by the determination section, with a higher priority than that utilized in the case of imaging data pertaining to an object of surveillance in which no status change is determined to have arisen.