An earpiece, an electronic device, and a communication device, capable of reducing the influence of leakage of sounds from a clearance between the earpiece and an ear not to need an addition of parts are provided. An earpiece (100) includes an electromechanical acoustic transducer (10) having a diaphragm and for generating a sound by vibrating the diaphragm in response to an electric signal, a case (11) on which a sound hole (12) is provided and in which the electromechanical acoustic transducer (10) is housed, and a holding member (13) for holding the electromechanical acoustic transducer (10) in the case (11). The electromechanical acoustic transducer (10) has a sound pressure-frequency characteristic that is compensated in advance such that the sound pressure-frequency characteristic is planarized in a condition that the generated sound is leaked from a user's ear (14) being covered with the case (11).