A side recording system for gaining device is intended for side recording of a gaming machine platform and mainly functions such that beginning and ending of event of gaining machine platform is monitored by a game state monitoring device to control an image acquisition device to acquire images of a game display unit and generate side-recorded videos, stored into a data storage unit, indicative of game session numbers and events; or a continuously side-recorded video can be recorded continuously, beginning and ending time points of event together with associated positions of beginning and ending time points of event corresponding to the continuously side-recorded video are recorded by an association recording unit, and an association recording table and the continuously side-recorded video are stored into the data storage unit. Thus, management staff can retrieve the required side-recorded videos rapidly to show what actually happens at once and take appropriate counter measures.