This thesis is exploring the ideology of filial piety of not forsaking the old people taught in the Buddha dharma on the basis of the Sūtra of Saṃyuktaratna-piṭaka which holds the statement on the occasion of a son and an old father. The story went in the sutra that there was a violation towards the law of “forsaking the old” by a courtier and he behaved stilly in filial piety, which touched the god. Then the god questioned the king of the country. It seemed not so easy to be answered about the question and even nobody can offer the reply in the whole country. Right at the moment, the courtier went back home to ask his father about the question lifted by the god. And the father told his son-the courtier saying “It is easy for that………..” Hence, the questions raised by the god towards the king were entirely solved by the old father. Apparently the king didn’t know who gave the answers to solve the questions. Thereafter the courtier told the king that it was the wisdom of his father hidden in the underground cave to solve the questions. After that, the king rescinded the law of forsaking the old and declared that everybody in the country ought to practice the filial piety to respect the old persons. There are three points asserted in this thesis which are very different from the preceding researchers. 1). The point of the thesis is to narrate the cruciality of filial piety according to the story of forsaking the old cited in the sutra and to elucidate the causality of filial behaviors. 2). The thesis is pivoting on “The Sūtra of Saṃyuktaratna-piṭaka” and then adding the other sūtras such as “The Sūtra of Bodhisattva Precepts” and “The Ullambana Sūtra”to hold the testimonials in the research of the ideology of filial piety. It was the fact to consider that historically the practice of filial piety had a great deal of influences on the descendant under the socio-cultural background in India and to compare the differences between the worldly and monastic understanding of the filial piety. 3). The story within "" Sūtra of Saṃyuktaratna-piṭaka."" is regarded as an ultimate aim of the filial piety of contemporary sons and daughters to their parents for the sustainable life. Thus, the value of this research is to arouse people paying attention to the ethics of the national, community and family as well as the malpractice of modern culture of filial piety. Then, it would be an important issue to melt the filial piety with Buddhists’ otherworldly philosophy into contemporary society and culture.