Abstract: A diaphragm body (12) is provided with a plurality of slits (14, 14a) extending from the central part thereof toward the outer circumference. The slits (14, 14a) are filled with a low-elasticity filling material composed of a material different from that of the diaphragm body (12). The slits (14, 14a) are extended rectilinearly or curvedly. The filling material (15) has a Young's modulus lower than that of the principal material of the diaphragm body (12) and/or an internal loss larger than of the principal material of the diaphragm body (12). Furthermore, the filling material (15) employs UV ray and/or visible ray curable resin or thermoplastic resin. Alternatively the filler (15) may be a porous material or a foamed material. The diaphragm body (12) produced by filling the slits (14, 14a) with the filling material (15) is employed for constituting a loudspeaker.