PURPOSE: To form frames for attaching filters, which is made of a disposable material by incineration, or the like together with the filters and is made from a metal.

CONSTITUTION: Frame materials 2, 3 are each placed in the vertical direction on an inside edge and outside edge of partial frames up and down which are framed square with a slender strip, and a core constituting material 5 is arranged at inside of the space thus formed from these assembly so as to have stiffness. All of them are made of paper. Namely the assembly can be defined as frames framed square with squared lumber of paper having a square cross section.