PURPOSE: To obtain a valve body for a reflux device of waste gases (EGR valve body) without using any core by charging molten metal into a mold disposed with a metallic reflux pipe for waste gases and insert-casting said pipe.

CONSTITUTION: An investment casting pattern 11a consisting of a reflux pipe 22 for waste gases and foamed polystyrene, etc. is disposed in the prescribed position in a mold consisting of a cope 6 and a drag 7 molded respectively of molding sand 6a, 7a. The molten metal M produced in a melting furnace is charged through a sprue not shown into the mold, and the metal M is fed through runners and gates to the pattern 11a. Therefore, only the pattern 11a is burned away by the metal M, whereby a cavity 11b is formed. The metal M is filled in the formed cavity 11b to cast the metal around the pipe 22. The casting is finished, whereby the intended EGR valve body is obtained.