1. A method for performing machine translation using a translation apparatus having a processor, the method comprising: receiving, using the processor, a plurality of respective candidate target texts which are generated by translation of a source text in a first language into a target text in a second language different from the first language as candidates for the target text in the second language; specifying, using the processor, combinations of phrase pairs used to generate the respective candidate target texts among phrase pairs contained in a phrase table of a translation model, the phrase table stored in a server and containing the phrase pairs each being a pair of a phrase in the first language and a phrase in the second language; and recording, using the processor, combination information in the server, the combination information identifying the combinations of phrase pairs, wherein the phrase pairs contained in the phrase table of the translation model are respectively associated with scores each of which is information on probability of occurrence of the phrase pair associated therewith, the method further comprising: prompting a user to select a most suitable candidate target text from the candidate target texts; using the recorded combination information, identifying the combination of the phrase pairs used to generate the candidate target text not selected in the selecting; evaluating each of the phrase pairs forming the identified combination so as to adjust a score of the phrase pair; updating the translation model by learning the adjusted score of the phrase pair; and retranslating the source text using the updated translation model.