An actuator includes a diaphragm, a lower electrode on the diaphragm, an electromechanical transducer film on the lower electrode, and an upper electrode on the electromechanical transducer film. The diaphragm includes a first silicon oxide film having a thickness of 0.5 μm or more, a silicon layer on the first silicon oxide film, a thickness of which is 3 μm or more, and a second silicon oxide film on the silicon layer, a thickness of which is 0.5 μm or more. A volume resistivity of the silicon layer is 103 Ω·cm or more and 106 Ω·cm or less.