An electronic includes a memory, a photosensitive element, and a processing element. The photosensitive element receives light beams and generating trigger signals when intensity of the received light beams reach a predetermined value. The processing element electrically connected to the photosensitive element and the memory, counts a number of disassembly times of the electronic device according to the times the trigger signals have been generated by the photosensitive element and stores the number in the memory.