A casing for covering an outer yoke is provided; an acoustic cavity is formed by this casing; a diaphragm and the outer surface of a side wall of the outer yoke; a second elastic member is provided to join the outer circumferential edge of the casing to the outer circumferential edge of the diaphragm without any gap therebetween; this second elastic member includes pores formed by foaming and made of a material whose elastic modulus is smaller than that of a first elastic member; and pores communicating through from the back surface of the second elastic member, that is the inner side of the casing, to the front surface that is the opposite side of the back surface are eliminated.