Disclosed herein is an adapter and an electronic system. The adapter includes a power cable, a converter arranged on one end of the power cable, and a connector arranged on another end of the power cable and configured to be connected to an electronic device, and the connector includes a connector body formed in a cylindrical shape and an inside of which includes a hollow portion, a first adapter terminal arranged on a circumferential surface of the hollow portion of the connector body, and a second adapter terminal arranged on a circumferential surface of the connector body, and configured to have a power capacity different from a power capacity of the first adapter terminal.