Provided is a self-running type scanner comprising a movable scanner unit (1′) and a running guiding and assisting plate (23) mounting the scanner unit for guiding running of the scanner unit. The movable scanner unit comprises an illuminating light source (10), a step motor (46) from running the scanner unit, an image sensor (13), a controller (20) for controlling provision of image information and running of the scanner unit, and wheels (21, 22) to which the rotation force of the motor is transmitted. The running assisting plate comprises guides (33a, 33b) engaging with the wheels, a light transmitting area (34), a white area (35) around the light transmitting area, a black area (D) surrounding the white area and the light transmitting area, and timing marks (36, 37) indicative of the position for starting reading.