An acoustic device according to the present technology includes an operating portion and a control unit. The operating portion generates information for determining whether a state of an earphone portion is a wearing state in which the earphone portion is worn by the user, or a non-wearing state in which the earphone portion is not worn by the user. The control unit determines whether the earphone portion is in the wearing state or in the non-wearing state on the basis of output from the operating portion, and implements a function based on a result of the determination.