An investigation assist device includes a processor and a storage that records information on a road map including a plurality of intersections and captured videos of a plurality of cameras respectively in correlation with a capturing time, camera information, and intersection information. The processor retrieves a vehicle satisfying a retrieval condition based on a captured video of the camera specified by camera information corresponding to designated intersection information specifying at least one intersection of the plurality of intersections. The processor superimposes a traveling direction of a selected vehicle at the time of passing through an intersection corresponding to the designated intersection information on a position of the intersection on the road map in response to selection of the information on the vehicle.