Abstract: In order to reliably form a coating layer on the interior surface of a primary lining such as an underground pipe, etc., in a short time and form a coating layer having a uniform thickness, a spray gun 62 is attached to a revolving ring 30 attached to a running truck 2, right and left drive wheels of the running truck 2 are respectively independently driven and controlled to moving the running truck 2 in a primary lining 90 while the revolving ring 30 is rotated at a steady peripheral velocity to blow out a coating material from the spray gun 62, whereby a homogenous coating layer is formed with a fixed thickness on the interior surface of the primary lining 90.