A drive assist device allows a driver to favorably check space for opening a back door along with an image of a periphery of a vehicle. The drive assist device is configured: to perform a viewpoint conversion that converts an image captured by a vehicle-mounted camera, which image is of a scene in the periphery of the vehicle including at least an area rearward of the vehicle, into an overhead image showing the vehicle from above; to superimpose on the overhead image a graphic image showing a flip-up back door in an open state from the same viewpoint as that of the overhead image; and to allow the superimposed image to be displayed on a monitor device in a vehicle compartment.