An investigation assist system includes an investigation assist device that acquires captured video of cameras installed at a plurality of intersections respectively; and an operator terminal that is connected to the investigation assist device so as to communicate with the investigation assist device. The investigation assist device detects an occurrence of an event at a first point based on the acquired captured video of the camera, and transmits the captured video of the camera to the operator terminal, the captured video being acquired at a time when the event is detected. The operator terminal records the captured video of the camera transmitted from the investigation assist device, and transmits report contents information based on the report indicating the occurrence of the event to the investigation assist device. The investigation assist device extracts a captured video satisfying the report contents information transmitted from the operator terminal, and transmits the extracted video to the investigation assist device. The operator terminal displays the captured video transmitted from the investigation assist device on the display.