PURPOSE: To surely fix a net to the front frame of a speaker box by forming a groove on the front peripheral edge of the front frame of the speaker box, inserting the outer peripheral edge of the net into the groove, dissolving at least the speaker box, and fixing the net and the speaker box with each other.

CONSTITUTION: After a speaker box 1 is arranged by directing its groove 3 upward, the groove 3 is covered with a protecting net 4. Next, a jig 5 is inserted into the groove 3 from the upper surface of the protecting net 4. The protecting net 4 keeps moderate net tension by the frictional resistance between the inner wall surface of the groove 3 and the contact part of the jig 5. After the jig 5 is pushed in until the protecting net 4 contacts on the bottom part of the groove 3, a thinner solvent 6 such as a methyl ethylene ketone is injected in the groove 3. The solvent diffuses by the capillary phenomena of the inner wall of the speaker box 1, the protecting net 4, and the jig 5 and widely dissolves the speaker box 1 and the protecting net 4.