A delivery assistance device assists in an operation of a delivery service in which the inside of a vehicle, a building, or a facility that is used by a purchaser is designated as a delivery destination of one or more products purchased via a predetermined website regarding electronic commerce. The delivery assistance device includes a controller configured to transmit delivery destination information on the vehicle, the building, or the facility for designating the inside of the vehicle, the building, or the facility that is used by the user as a delivery destination of the product to an external device or a terminal at which the user browses the website when the controller receives user information indicating that the user intends to order the one or more products in the website from the external device operating the website.