An adapter apparatus for an earphone accessory is provided. The adapter apparatus includes an earphone jack, a connection interface, a pre-amplifier and a device adapter circuit. The earphone jack is suitable for a plug of the earphone accessory to plug in. The connection interface is suitable for being electrically connected with a portable device. The pre-amplifier is electrically connected to the earphone jack to receive an earphone control signal of the earphone accessory and to provide an amplified earphone control signal. The device adapter circuit is electrically connected to the pre-amplifier and the connection interface to receive the amplified earphone control signal of the earphone accessory and provide a device control signal to the portable device via the connection interface.