Provided is a vehicle driving assist device which can clearly display superimposing guide lines on an image captured from the surrounding area of a vehicle without increasing the areas of the superimposing lines. The vehicle driving assist device displays an image captured from the surrounding area of a vehicle on a vehicle monitor. The vehicle driving assist device comprises: an imaging unit mounted in a vehicle for capturing the image from the surrounding area of the vehicle; and an image processing unit for displaying superimposing guide lines on the image output from the imaging unit. The image processing unit displays the guide lines in a manner such that colors are periodically altered in the length directions thereof and displayed.