A drive recorder sends to a server a moving image file showing a situation of surroundings of vehicle in a moment at which large acceleration occurred. The server determines, based on moving image file, whether or not to prohibit from being overwritten moving image file showing surroundings of vehicle in a moment at which an event occurred. Based on a determination result determined by the server, the drive recorder prohibits from being overwritten an image data set showing the moment 1) at which the event occurred or 2) optionally before and/or after the event occurred including the moment at which the event occurred. Thus, the drive recorder can surely prohibit the image data set to be prohibited from being overwritten. Moreover, it is possible to effectively use a storage area of a memory by allowing overwriting image data set that does not necessarily need to be prohibited from being overwritten.