PURPOSE: To enhance manufacturing efficiency by a method wherein continuous punched plates are respectively fixed to the opposed surfaces of the upper and lower frames of a square frame to form bent shallow grooves on the opposed surfaces and the bottom surfaces of the bent shallow grooves are coated with an adhesive and, subsequently, the end surfaces of a filter medium are bonded and fixed to the bottom surfaces of the bent shallow grooves.

CONSTITUTION: Continuous punched plates 3a, 3b are respectively fixed to the mutually opposed surfaces of the upper and lower frames 1a, 1b of a square frame 1 to form bent shallow grooves 4 between the continuous punched plates 3a, 3b. Adhesive layers 5 are formed to one side surfaces of the continuous punched plates 3a, 3b and release papers 6 are bonded to the surfaces of the adhesive layers 5. When the punched plates are fixed to the upper and lower frames 1a,1b, the release papers 6 are peeled off to fix the punched plates to the upper and lower frames through the adhesive layers 5. Next, the bottoms of the bent shallow grooves 4 are coated with an epoxy resin type adhesive 9 and the end surfaces of a filter material 2 are bonded and fixed to the bottoms of the bent shallow grooves 4 through the adhesive 9 to obtain a filter. By this method, the manufacturing cost can be reduced.