PURPOSE: To make foaming of a base part of a foamed object uniform under the condition of free foaming, by providing a lattice etc. so as to cover an entire or more than half part of expanding directions when a resin foams and making the resin to foam directing from its inside to an outside.

CONSTITUTION: In order to fill e.g. an inside part of a vibrating plate 1 of a cone type speaker with a resin 4 and to foam it, after an entire part or more than half part of expanding directions from a shaped or flat base in foaming of the resin 4 being covered by a flat or shaped lattice or net 3, the resin 4 is foamed from its inside to an outside. Then, the resin 4 is cut between the net 3 and an opening part of the vibrating plate 1 after the resin solidifies and an excess 5 of the resin is removed and an inside part surrounded by the vibrating plate 1 and the net 3 is used.

EFFECT: Effect of contraction of resins inside and outside of a lattice etc. is small.

USE: A cone type speaker.