PURPOSE: To automate the steering and position control of a work device without setting a conductive body newly on a travel road surface.

CONSTITUTION: A pair of ultrasonic wave sensors 9 are provided opposedly to a frame body 7 provided along the advancing direction of an asphalt finisher, and a lateral displacement detection device 11 to detect the lateral displacement of the asphalt finisher by a distance to the frame body 7 or travel road surface 8 detected by these ultrasonic wave sensors 9. Based on the lateral displacement detected by the lateral displacement detection device 11, a steering control device 13 to modify the steer angle of front wheels and a screed control device 12 to modify the lateral position of a screed part as a work device are provided. Thus steering can be automated, and also the position control of the work device can be automated to save labor. Also it becomes unnecessary to set a conductive body and conductive transmission device newly on a travel road surface 8 to reduce work cost and to improve work efficiency.