The present application provides a human joint energy harvesting apparatus for capturing the biomechanical energy of a joint to generate electrical energy. The generated electrical energy may provide a real-time power supply to the wearable electronics. The apparatus employs a linear slide rail mechanism and cooperates with the user's first limb and second limb to form a slider-crank mechanism, which converts the rotating motion of the joint into a linear motion of the linear slide rail mechanism. The bending beam converts the linear motion of the linear slide rail mechanism into a bending motion. A piezoelectric film may be bonded to the upper and lower surfaces of the bending beam. During walking, the bending beam is deformed, causing the piezoelectric film to be stretched or compressed to generate electrical energy. To harvest more energy, the bending beam used in the apparatus is designed to be subjected to forced motion and free vibration, and a proof mass is attached to it. The present application also provides a wearable electronic device equipped with the human joint energy harvesting apparatus.