In this paper we report a way of constructing a translation corpus that contains not only source and target texts, but draft and final versions of target texts, through the translation hosting site Minna no Hon'yaku (MNH). We made MNH publicly available on April 2009. Since then, more than 1,000 users have registered and over 3,500 documents have been translated, as of February 2010, from English to Japanese and from Japanese to English. MNH provides an integrated translation-aid environment, QRedit, which enables translators to look up high-quality dictionaries and Wikipedia as well as to search Google seamlessly. As MNH keeps translation logs, a corpus consisting of source texts, draft translations in several versions, and final translations is constructed naturally through MNH. This corpus can be used for self-learning by inexperienced translators on MNH, and potentially for improving machine translation.