IMAGE FORMING DEVICE AND IMAGE FORMING METHOD

An image acquisition unit acquires camera images obtained by cameras, which are configured to photograph a periphery of the vehicle. An image synthesizing unit projects data of the camera images on a virtual projection surface, which corresponds to the periphery of the vehicle, and forms a synthetic image showing the periphery of the vehicle, which is viewed from a virtual view point, by using the data projected on the projection surface. A travelling-environment determination unit determines whether a travelling environment of the vehicle is an off-road or an on-road based on a signal from an other on-board device of the vehicle. The image synthesizing unit is configured to change a shape of the projection surface, which is for forming the synthetic image, according to whether the travelling-environment determination unit determines that the travelling environment is an off-road.