This paper purposes to clarify the significance of the concept of vulnerability in bioethics and to rethink the view of human beings through reviewing the main international documents regarding research ethics in biomedicine; the Belmont Report, Guidelines of CIOMS, Barcelona Declaration, the versions of Helsinki Declaration of WMA, and the documents of UNESCO. From our review the following conclusions can be derived. Firstly, it is only since the 90’s that the concept of vulnerability has been used as an important key concept. Secondly, there are great differences in the concept of vulnerability among CIOMS, WMA, and UNESCO. The former two have the same schema as the Belmont Report, that is, the one that both CIOMS and WMA have the ideal of individual autonomy and view the vulnerable research subjects as objects of special protection. In contrast, the latter distinguishes intrinsic universal vulnerabilities of human beings from ones of special groups or persons, and supports autonomy of them. Behind those great differences lies a differing viewpoint from the Anglo-American view of bioethics to the European one; a difference between the conception of bioethics as human-based medicine ethics and the one of bioethics as “ethics of life” including other lives and natural environment. Thirdly, however, in the documents of UNESCO how these two vulnerabilities relate to each other, remains ambiguous. Lastly, a view of universal vulnerability prompts us to change the mainstream view of “autonomous individual” / “individual autonomy” into the one of “relative individual” / “relative autonomy”. We should therefore also revisit the concept of “human dignity” and “respect for person”.