This invention is to provide a tunnel detection technique, which is hardly affected by external circumstance at each time. A roadway type judgment method according to the invention includes: calculating, with respect to image data from a camera mounted in or on a vehicle or image data obtained by carrying out a specified conversion on the image data from the camera, a feature amount of at least one component among plural components in a specified color space of the image and storing the calculated feature amount into a feature amount data storage; determining whether or not the feature amount stored in the feature amount data storage satisfies a predetermined condition; based on a determination result at the determining, judging whether or not the vehicle travels inside a tunnel.