This paper proposes a synthesizing methodology of developing a robotic skill for task execution. Specifically, the paper addresses how to improve reusability of the skill to use it on various robotic systems. First, a skill acquisition system based on human demonstration as well as a skill acquisition method are described. Second, how to improve the reusability of the skill is discussed to obtain a robotic task skill with high reusability. Third, a reusable skill execution system is designed and implemented. Finally, a task skill is developed for a practical task by using the proposed method to experimentally validate the reusability of the skill.