An input device of an embodiment includes a ring portion (operation body) which has a substantially circular cross-section, of which an outer peripheral surface is used as an operation surface, and which is twist-operated in a cross-section circumferential direction thereof, first sensor members to detect operation position information on the operation surface, second sensor members to detect twist information when the twist operation is performed, and a controller to output the operation position information based on electric changes of the first sensor members and the twist information based on electric changes of the second sensor members, in order to control activation of an electronic device.