Provided is a method for welding a plate member on a base plate. The method includes: a step for preparing a base plate; a step for forming a pair of guide pieces on the base plate; a step for forming a plate member by using a clamp between the guide pieces; a step for conducting a tack welding between the base plate and the plate member while supporting the plate member using the clamp; and a step for removing the clamp from the base plate.
