[Problem] To provide an accident prevention system which prevents collision accidents, while minimizing the number of monitoring devices, in order to reduce the workload and the cost burden. [Solution] This accident prevention system 1 is provided with an imaging device 10, a monitoring server 20, and a warning device 60. A control unit 30 of the monitoring server 20 executes an area reception module 31, to receive an input of an approach area which a vehicle is approaching and a risk area which is risky for the vehicle to approach, in a basic image captured by the imaging device 10. Furthermore, the control unit 30 executes a first determination module 33, to determine whether the vehicle has entered the approach area, using an image captured by the imaging device 10. When the vehicle has entered the approach area, the control unit 30 executes a second determination module 34, to determine whether a person or the like has entered the approach area or the risk area. Furthermore, if a person or the like has entered the approach area or the like, the control unit 30 executes a warning module 35, to instruct the warning device 60 to provide warning information.