The present disclosure provides a miniature speaker, including a vibration unit, a magnetic unit and a housing, the vibration unit includes a first diaphragm, a centering support, a second diaphragm and a voice coil; the centering support includes a first centering support and a second centering support having a conductive portion electrically connected with an external circuit; the second diaphragm includes a first half-diaphragm assembled with the first centering support and a second half-diaphragm assembled with the second centering support, the first half-diaphragm and the second half-diaphragm are asymmetrical configured with respect to each other. Under such structure, it is only necessary to adjust the material and shape of the first half-diaphragm and the second half-diaphragm, swing of the miniature speaker at low frequency can be effectively suppressed, a maximum output sound pressure of the miniature speaker can be effectively improved, and low-frequency sound quality can be improved accordingly.