There are provided a driving assistance device and a computer program that allow, when a vehicle is parked in a parking lot, deriving of a travel path from an entrance to the parking lot up to the point where the vehicle is parked in a parking space, the travel path identifying specific travel locations in the parking lot. Specifically, it is configured such that when a vehicle is parked in a parking lot, layout information of parking spaces provided in the parking lot is obtained and a parking location where the vehicle is parked is obtained from among the parking spaces, an intra-parking-lot network which is a network representing a route that can be selected by the vehicle in the parking lot is obtained, a travel path from an entrance to the parking lot up to the point where the vehicle is parked in the parking location is generated using the intra-parking-lot network and the layout information of parking spaces, the travel path identifying vehicle's travel locations in the parking lot, and driving assistance based on the generated travel path is provided.