To make a case part repeatedly usable, by forming a filter in a constitution including a case body, a cover body detachably provided in the case body, and a filter body detachably provided in a case so that the filter body in the case only can be replaced.

A sending hole is provided at the center of a closing plate of a cylindrical case body 1 having a closed end, and introducing holes 1d, 1d are provided around the sending hole at regular intervals. A filter body 2 is formed from a supporting member 3 comprising a cylindrical body of punching metal and a filter material 4 comprising a cylindrical folded filter paper. A bowl-shaped cover body 5 is attached to the opening side of the body 1. The filter is disassembled by removing the cover body 5, pulling the body 2 out of the body 1, and drawing the filter material 4 out of the member 3. Therefore, a case part can be repeatedly used and in the filter body 2, the combustible filter material 4 is separated from the noncombustible supporting member 3 so that the member 3 can be reused, and hence landfilling for waste disposal is not required.