Abstract: A double cylinder shaped multilayer structural member comprising ring shaped thin plate small diameter discs and large diameter discs respectively layered via spacers is disposed in the enclosure vessel of a trap device for a vapor phase reaction apparatus. Gas from the intake opening section of the enclosure vessel is introduced into the outer side space of the multilayer structural member of the enclosure vessel, passes through the spaces between the large diameter discs and also passes through the spaces between the small diameter discs, then exits via the inner side space of the multilayer structural member from the outlet opening section of enclosure vessel to the system exterior. As a result of this construction, in comparison to conventional devices, the collection efficiency of reactive components can be increased, the equipment life extended, and maintenance frequency reduced, thereby providing a trap device for a vapor phase reaction apparatus capable of improving productivity.