Mechanical energy is known to be transferred between a body segment and a joint. However, the transformation of this energy has not been classified. By focusing on the racquet-holding arm during a tennis serve, the present study examined the transformation between translational and rotational energies due to the joint force, and investigated the kinetic chain from the viewpoint of energetics. Twenty-two tennis players were asked to perform flat services to the deuce side (i.e., the receiver's right side), and the three-dimensional coordinates of reflective markers attached to each player and racquet were collected with a motion capture system. The mechanical power acting on each segment and the mechanical energy generated/absorbed by each joint were divided into the following components: (1) STP =the time rate of change in the rotational energy of a segment due to the joint torque, (2) JTP =the generation/absorption of rotational energy due to the joint torque, (3) JFP _t=the time rate of change in the translational energy of a segment due to the joint force, and (4) JFP _r=the time rate of change in the rotational energy of a segment due to the moment of the joint force. The findings are summarized below. 1. The proposed method can divide the power acting on the segment due to joint force into the translational component ( JFP _t) and the rotational component ( JFP _r). 2. The racquet-holding arm mainly acquires mechanical energy as translational energy with decreasing rotational energy of the upper trunk (around right-leftward rotation). 3. The main role of the shoulder joint is not to generate rotational energy but to change the energy form (from translational energy to rotational energy). 4. The main role of the phase before most of the shoulder external rotation is to store the translational energy in the racquet-holding arm. 5. The main role of the phase after most of the shoulder external rotation is to transfer the translational and rotational energies to the racquet. 6. The proposed method can quantify not only the generation/absorption and transmission of mechanical energy but also the transformation of the energy form. Therefore, this method may produce new findings that have not yet been clarified.