A diaphragm is provided, including a dome and a suspension extending from a periphery of the dome. The dome includes a stack of an aluminum foil layer, a foam layer and a carbon fiber layer. The dome is recessed from the aluminum foil layer toward the carbon fiber layer to form a receiving recess. The receiving recess is arranged surrounding the periphery of the dome. The suspension is partially received in the receiving recess and is fixed to the dome. A sounding device is also provided, the sounding device includes the diaphragm. The diaphragm and the sounding device of the present disclosure have better high frequency acoustic performance and excellent reliability.