The purpose of this study was to evaluate the generation, absorption and transfer of mechanical energy during baseball batting, focusing on the lower extremities and torso. The batting motion and ground reaction forces acting on each foot of 79 amateur baseball players were recorded using a motion capture system and 2 force plates. The joint forces and joint torques were calculated using inverse dynamics. In addition, the mechanical powers as a function of each joint torque were calculated to assess the generation/absorption of mechanical energy. The mechanical powers as a function of joint forces and joint torques acting on each segment were calculated to assess the transfer of mechanical energy. The main results were as follows: 1. In the phase from contact of the stride foot to the peak lower torso rotational velocity (lower torso acceleration phase), the mechanical energy was generated and flowed into the lower torso as a function of hip joint torque. 2. In the lower torso acceleration phase, the mechanical energy flowed out from the lower torso to the upper torso as a function of torso joint torque. 3. In the phase from the peak lower torso rotational velocity to impact (swing phase), the mechanical energy was generated and flowed into the upper torso as a function of torso joint torque. 4. In the swing phase, the mechanical energy of the bat increased rapidly, and this amount of change was significantly correlated with the bat head speed at impact. 5. Though the analysis phase, the change in the mechanical energy of the torso was small. These results suggest that both hip joints generate mechanical energy and that the torso acts as a pathway of mechanical energy during baseball batting. In addition, the transfer of mechanical energy from the torso to the upper extremities and the bat contributes to increasing the bat head speed at impact.