A portable electronic device includes a body, a flippable unit, a pivoting shaft, a first magnetizable element, a second magnetizable element, a magnetic induction sensor IC, and a magnet. The pivot shaft connects the body and the flippable unit. A display is disposed in the flippable unit for showing an image. The magnetic induction sensor IC is disposed in the body. The magnet is disposed at and rotatable with the pivoting shaft. The first and the second magnetizable elements are disposed between the magnet and the magnetic induction sensor IC to enlarge the magnetic field of the magnet such that the magnetic induction sensor IC is capable of detecting change of the magnetic field of the magnet when the flippable unit together with the magnet is pivoted relative to the body.