A diaphragm for use in a speaker is manufactured using a plurality of thin wooden boards having flat rectangular shapes. The thin wooden boards are impregnated with a resin; then, a plurality of cutouts, which are elongated along wooden fiber directions or which are elongated in directions crossing wooden fiber directions, are formed in the thin wooden boards. Instead of the cutouts, it is possible to form a plurality of folded portions elongated in directions crossing wooden fiber directions. The thin wooden boards are integrally laminated together in such a way that the wooden fiber directions thereof mutually cross with a prescribed angle therebetween. The thin wooden boards integrally laminated together are subjected to thermal pressing so as to form a wooden vibrator serving as the diaphragm. Thus, it is possible to easily produce the diaphragm having a high strength and superior acoustic characteristics without causing defects.