A portable electronic device that can operate even when electric power supplied through contactless charge by electromagnetic induction is low is provided. The portable electronic device includes a reflective liquid crystal display which includes a transistor including an oxide semiconductor, a power source portion which includes a rechargeable battery capable of charge by contactless charge, and a signal processing portion which includes a nonvolatile semiconductor memory device. In the portable electronic device, electric power stored in the rechargeable battery is used in the reflective liquid crystal display and the signal processing portion.