An earphone including a housing, a speaker, a tuning mechanism and an acoustic damper is provided. The housing has a sound-output opening. The speaker is disposed at the sound-output opening. The speaker and the housing together define a compartment. The speaker has an inner chamber and a through hole for communicating the inner chamber and the compartment. The tuning mechanism is movably disposed at the housing and extended into the compartment. The acoustic damper is disposed between the tuning mechanism and the speaker, and located at the through hole. The tuning mechanism is configured to move to compress or release the acoustic damper for adjusting the air permeability of the acoustic damper.