PURPOSE: To automatically construct a firm protective shoulder by allowing a self-propelled shoulder banking forming machine to seed turfs over a shoulder section in parallel with shoulder banking forming works.

CONSTITUTION: A seeding machine 30 including a seed tape roll 31 where the seeds of turves and the like are held in a tape, and soil covering screw 36 which pulls a seed tape 31b out of the a roll so as to cover the tape with banking material, is mounted on the rear side of the movable hopper 20b of a mobile type shoulder banking forming machine. In order to sow seeds using the forming machine, the banking material is supplied to a banking forming hopper 20 first, and a truck 1 is concurrently run along a shoulder line, so that the banking material is discharged out of the bottom surface of the movable hopper section 20b over the floor of a shoulder. In this case, the seed tape 31a is pulled out to a low laid and smoothed surface set in advance, so that the projected section of the laid and smoothed baking material is pushed and spread by the soil covering screw 36 so as to let the tape be covered with the banking material.