Huge amount of mechanical energy generated by continuous human motion usually is abandoned. Among technologies that convert such abandoned mechanical energy into reusable electrical energy, the triboelectric nanogenerators (TENGs) has many advantages. These TENGs can be used in electronics for human body implants, but the amount of mechanical energy (heartbeat, blood flow, muscle movement) generated inside the human body is very small and the amount of energy converted might be negligible. While, since TENGs are a power generation device using mechanical energy, research on application to the human body is still intensively ongoing worldwide. The highest mechanical energy potential of a person's movement is the mechanical energy due to the upward and downward movement that occurs when a person walks, and cannot be ignored if one adult walks more than 5,000 times a day. If devices capable of harvesting mechanical energy by up-and-down movements are developed, they can be operated as wearable, e-skin, and various sensors and device power supplies for implanted electronics and battery charging supporters. We have developed a device that is optimized based on inertial principle of mechanical energy generated when a person is walking. Assuming a displacement of about 6.3 cm when a person walked, the inertial-based TENG produced a voltage of about 220 V and a current of 45 µA in a single-layer device. Since the developed inertial-based TENG is very easy to be stacked, it can be stacked up to multiple layers, and the voltage characteristics of about 380 V and the current characteristics of 85 µA are reached in the three - layer stacked inertial-based TENG. To verify the feasibility of this level of inertial-based TENG as an energy source at a usable level, the output characteristics were verified by implanting live animals (dogs). In addition, the conversion of mechanical energy generated by the movement of the animal into electrical energy was verified in real time through the integrated Bluetooth. Our approach is expected to have a significant impact on a wide range of applications in biomedical biomedicine as a simple, cost-effective and high energy density output.