To easily retrieve an image related to a specified operation of a POS terminal out of monitored images recorded over a long time in a recording medium.

A POS terminal 11 transmits a processed content signal to an execution record generator 14 in every time when various kinds of processing contents such as receipt-of-money/payment processing, door opening processing are executed. The record generator 14 generates an execution record arrayed time-serially with processed content identifying informations in response to the processed content signal, and transmits it to a monitored image recorder 16. The image recorder 16 synchronizes the processed content identifying informations with image data to be added to header information of each frame, and records thereby the image data and execution records in the recording medium 15. As a result thereof, an image data table wherein the processed content identifying information is correlated with the image data is recorded in the recording medium 15.