In this chapter, we present a protocol for collaborative translation, where two non-bilingual people who use different languages collaborate to perform the task of translation using machine translation (MT) services. The key idea of this protocol is that one person, who handles the source language and knows the original sentence (source language side), evaluates the adequacy between the original sentence and the translation of the sentence made fluent by the other person, who handles the target language (target language side). In addition, by determining whether the meaning of the machine-translated sentence is understandable, it is ensured that the two non-bilingual people can do the above tasks without stopping the protocol. As a result, this protocol 1) improves MT quality; and 2) terminates successfully only when the translation result becomes adequate and fluent. An experiment shows that when the protocol terminates successfully, the quality of the translation is increased to about 83 percent for Japanese-English translation and 91 percent for Japanese-Chinese translation. We contributed to the Language Grid Project by proposing a new way to use MT services efficiently in real fields.