An adapter comprising: an adapter body comprising an adapter pin; a mounting portion provided in the adapter body and comprising a first mounting portion provided on one side of the adapter body on which the adapter pin is disposed, and a second mounting portion provided on another side of the adapter body; and a plug configured to be removably coupled to the first mounting portion and the second mounting portion in either a first orientation or a second orientation with respect to the mounting portion, wherein the plug comprises: a plug terminal (120, 420) provided on one side surface of the plug and electrically connected to the adapter pin provided on the one side of the first mounting portion regardless of the orientation of the plug with respect to the mounting portion; a plug body comprising a first plug body on which the plug terminal is disposed, the first plug body comprising a first insertion portion, and a second plug body extending from the first plug body in a direction different from a direction in which the first plug body extends, the second plug body comprising a second insertion portion; characterised in that the plug further comprises: a socket comprising a first socket provided on the first plug body and a second socket provided on the second plug body, and configured to allow the adapter pin to be inserted into the second socket passing through the second insertion portion when the plug terminal of the plug is in the first orientation, and inserted into the first socket passing through the first insertion portion when the plug terminal of the plug is in the second orientation; and a connecting member arranged between the first socket and the second socket to electrically connect the first socket to the second socket. an adapter body comprising an adapter pin; a mounting portion provided in the adapter body and comprising a first mounting portion provided on one side of the adapter body on which the adapter pin is disposed, and a second mounting portion provided on another side of the adapter body; and a plug configured to be removably coupled to the first mounting portion and the second mounting portion in either a first orientation or a second orientation with respect to the mounting portion, wherein the plug comprises: a plug terminal (120, 420) provided on one side surface of the plug and electrically connected to the adapter pin provided on the one side of the first mounting portion regardless of the orientation of the plug with respect to the mounting portion; a plug body comprising a first plug body on which the plug terminal is disposed, the first plug body comprising a first insertion portion, and a second plug body extending from the first plug body in a direction different from a direction in which the first plug body extends, the second plug body comprising a second insertion portion; a plug terminal (120, 420) provided on one side surface of the plug and electrically connected to the adapter pin provided on the one side of the first mounting portion regardless of the orientation of the plug with respect to the mounting portion; a plug body comprising a first plug body on which the plug terminal is disposed, the first plug body comprising a first insertion portion, and a second plug body extending from the first plug body in a direction different from a direction in which the first plug body extends, the second plug body comprising a second insertion portion; characterised in that the plug further comprises: a socket comprising a first socket provided on the first plug body and a second socket provided on the second plug body, and configured to allow the adapter pin to be inserted into the second socket passing through the second insertion portion when the plug terminal of the plug is in the first orientation, and inserted into the first socket passing through the first insertion portion when the plug terminal of the plug is in the second orientation; and a connecting member arranged between the first socket and the second socket to electrically connect the first socket to the second socket. a socket comprising a first socket provided on the first plug body and a second socket provided on the second plug body, and configured to allow the adapter pin to be inserted into the second socket passing through the second insertion portion when the plug terminal of the plug is in the first orientation, and inserted into the first socket passing through the first insertion portion when the plug terminal of the plug is in the second orientation; and a connecting member arranged between the first socket and the second socket to electrically connect the first socket to the second socket.