A wearable device needs to have a design corresponding to complicated surfaces of human bodies. Thus, an electronic device that can fit the characteristics of each individual human body after being purchased and can be worn naturally and comfortably is provided. The electronic device includes a secondary battery which can be transformed. By using a secondary battery which can be transformed, for example, a secondary battery can be efficiently placed in a narrow and elongated space in the electronic device, and the elongated secondary battery can be bent together with the electronic device. Furthermore, the weight balance of the electronic device can be easily adjusted.