PURPOSE: To decrease the area of the inner wall face of an inner tube thereby reducing the quantity of the film grown on the inner wall face of the inner tube to prevent the adhesion of foreign matter to a board by providing the wall face of the inner tube with many holes.

CONSTITUTION: In an inner tube 11, which consists of quartz tube and is provided inside an outer tube 2, many round holes 11a are provided at the whole wall face. And the inside of the inner tube 11 becomes the reaction chamber for growing a film, and a reaction product grows as a film on the wafer being a substrate within this reaction chamber. But in this case, since many ports 11a are provided at the wall face of the inner tube 11, the area of the inwall of the inner tube 11 is much smaller than the conventional case. For this reason, the quantity of reaction products filming on the inner wall face of the inner tube by the long-term use also becomes small. Hereby, the quantity of foreign matter by the separation of the reaction products on the inner wall face of this inner tube 11 becomes small.