A diaphragm (400) of a speaker (100) includes a vibrating member having a substantially thin-plate shape and a base material disposed substantially at the center in a width direction of the vibrating member. The base material is formed by a woof group, a front diagonal thread group, a back diagonal thread group and a warp group, the groups being arranged so as to cross with each other and have axial directions different from each other. Accordingly, tensile strengths of the diaphragm (400) in the axial directions of the groups, i.e., tensile strengths in four directions, can be set to substantially the same. Accordingly, since the number of directions having substantially the same tensile strength is larger than conventional arrangements using triaxial fabrics, occurrence of deformation such as bending of the diaphragm (400) due to resonance can be prevented as compared to the conventional arrangements. Therefore, the speaker (100) capable of vibrating properly can be provided.