A roadway boundary detecting apparatus has an imaging device for taking picture images ahead of a vehicle, a picture image memory connected to the imaging device for storing the picture images, and a control unit connected to the picture image memory. The roadway boundary detecting apparatus further has a program executable on the control unit for calculating speed information for pixels of consecutive picture images taken by the imaging device, detecting lowest point positions in regions in which pixels having speed components continuously exist along a vertical direction, based on the speed information for the pixels, and determining whether a straight line that connects the lowest point positions is a roadway boundary.