An electronic device carried around by the user is desired to be used for a long period. In order to achieve this, a high-capacity battery may be incorporated. Since a high-capacity battery is large, its incorporation in an electronic device increases the weight of the electronic device. An electronic device used while being implanted in the body of the user, provided with an emergency power supply, is provided. In an electronic device provided with a plurality of batteries, a transmitting portion and a receiving portion conduct wireless charging among different batteries, and the battery to be charged or used is selected by a power supply management circuit depending on the circumstances.