PURPOSE: To improve utilization efficiency as well as film quality and to extend a soaking region by providing an inner quartz tube having gas blow-off holes of the same shape inside a reaction tube made of quartz and inserting a cantilever loaded with a substrate to be treated into this inner quartz tube while providing an inner cap sealing the inner quarts tube on the cantilever.

CONSTITUTION: The inside of an inner quartz tube 16 is exhausted through an exhaust hole 5 to be in the state of reduced pressure so that reaction gas does not enter an outer quartz tube 16 through a gap with an inner cap 19. Next, a flange 20 and the inner quartz tube 16 are provided with an insertion hole 21 and reaction gas is tightly sealed by a packing 22, while an injector is inserted into this insertion hole 21 so as to supply reaction gas into the inner quartz tube 16. Here, blow-off holes 15 are uniformly provided on the inside of the inner quartz tube 16 for blowing off reaction gas against the substrates 8 to be treated. In this way, CVD reaction is performed so that a reaction product is stuck to the inside of the inner quartz tube 16 to cause a fear of producing dust, the inner quartz tube 16 and the cantilever 17 are exchanged collectively so that a CVD device can be continuously used so as to improve utilization efficiency.