There is provided an acoustic device that can reduce muffled sound. The disclosed acoustic device includes a holder 103 that has one end abutting the inside of an inferior antihelix crus and other end abutting a depression between a tragus and an antitragus of a user's ear, and a human body vibration sound generator 10 that is held by the holder 103 and allows sound to be heard by the user in response to an audio signal as well.