A driving assist apparatus, comprising: an image receiving portion that receives a captured image of a periphery of a vehicle, captured by a vehicle-mounted camera; an image output portion that displays, on a display apparatus inside the vehicle, a display image formed by superimposing a guide image on the captured image, the guide image being configured by a guide display using a graphics image containing a guide line for assisting a driver with a driving operation of the vehicle; a storage portion that stores, as the guide display, at least a plurality of predicted course lines that have been generated in advance as graphics images for every predetermined steering angle, the predicted course lines each being the guide line for assisting the driving operation by showing a predicted course according to an actual steering angle of the vehicle in the captured image; and a guide image providing portion that at least acquires the predicted course line as the guide display from the storage portion according to an actual steering angle of the vehicle using offset values on respective two axes in a two-dimensional orthogonal coordinate system, forms the guide image using the acquired guide display, and provides the formed image to the image output portion, characterized in that the offset values on the respective two axes in the two-dimensional orthogonal coordinate system being computed based on a difference between actual coordinate values in the captured image and ideal coordinate values, the difference being obtained based on a rotation parameter of the vehicle-mounted camera according to an attachment position of the vehicle-mounted camera, a rotation angle of the captured image with respect to an ideal state of the captured image is taken as a rotation-related error in an optical system occurring when attaching the vehicle-mounted camera to the vehicle, the storage portion further stores graphics images showing the guide displays according to a steering angle of the vehicle, according to the rotation-related error in the optical system, and the guide image providing portion acquires the graphics image of the predicted course line from the storage portion according to an actual steering angle of the vehicle and a rotation parameter indicating the rotation-related error in the optical system occurring when attaching the vehicle-mounted camera to the vehicle. an image receiving portion that receives a captured image of a periphery of a vehicle, captured by a vehicle-mounted camera; an image output portion that displays, on a display apparatus inside the vehicle, a display image formed by superimposing a guide image on the captured image, the guide image being configured by a guide display using a graphics image containing a guide line for assisting a driver with a driving operation of the vehicle; a storage portion that stores, as the guide display, at least a plurality of predicted course lines that have been generated in advance as graphics images for every predetermined steering angle, the predicted course lines each being the guide line for assisting the driving operation by showing a predicted course according to an actual steering angle of the vehicle in the captured image; and a guide image providing portion that at least acquires the predicted course line as the guide display from the storage portion according to an actual steering angle of the vehicle using offset values on respective two axes in a two-dimensional orthogonal coordinate system, forms the guide image using the acquired guide display, and provides the formed image to the image output portion, characterized in that the offset values on the respective two axes in the two-dimensional orthogonal coordinate system being computed based on a difference between actual coordinate values in the captured image and ideal coordinate values, the difference being obtained based on a rotation parameter of the vehicle-mounted camera according to an attachment position of the vehicle-mounted camera, a rotation angle of the captured image with respect to an ideal state of the captured image is taken as a rotation-related error in an optical system occurring when attaching the vehicle-mounted camera to the vehicle, the storage portion further stores graphics images showing the guide displays according to a steering angle of the vehicle, according to the rotation-related error in the optical system, and the guide image providing portion acquires the graphics image of the predicted course line from the storage portion according to an actual steering angle of the vehicle and a rotation parameter indicating the rotation-related error in the optical system occurring when attaching the vehicle-mounted camera to the vehicle.