To facilitate the mount and to obtain a sound quality close to an ideal tone quality by forming a sheet member freely deformed to be a hollow shape and filling in packing to a box so as to attain a desired shape.

A box part 11, a buffle plate 12 and a pouring port 15 are formed integrally and a speaker box 10 is made of a sheet material freely deformed such as vinyl material or a polyamide (Nylon) material and formed to be an enclosed hollow shape in 2-ply in the inside and outside walls. A hole 13 through which a speaker main body is inserted at a mount of the speaker unit, a hole 14 to mount the speaker unit, and a pouring hole 15 are made to the buffle plate 12. In this case, the box part 11 made of the sheet material deformed freely is inserted to an inner space of a door 20 from an opening 22 of a door inner board. Then a gas filling (air) is poured from the pouring port 15 after the insertion to the hollow enclosed part to swell the hollow, then the desired speaker box 10 is formed.