An automatic record detection device and method for stop arm violation event, comprising: a plurality of image fetching units, to fetch external video signals; at least an analog-to-digital converter, to process said external video signal into digital data; a processor unit, to detect dynamic images of said digital data based on a set sensitivity value, when said set sensitivity value of said dynamic image of a violating vehicle fulfills an image block number, it determines said dynamic image to trigger a violation event, then generates said digital data based on said external video signal. As such, a user can search said dynamic images of said digital data by examining said triggered violation event, to find out license plate number of a violating vehicle, and sends it to an agency concerned for prosecution, thus saving enormous time and manpower in viewing and searching through said digital data.