1. A translation processing device comprising: a setting unit that classifies a plurality of languages into a number of language categories and sets a typical language for each of the language categories; an intra-category converting unit that performs, for each of the language categories, mutual conversion between a sentence described in a first language classified in a first language category and a sentence described in a first typical language of the first language category; an inter-category converting unit that performs mutual conversion between a sentence described in the first typical language and a sentence described in a second typical language; and an acquiring unit that acquires information of an input sentence, the first language corresponding to a language of the input sentence, and a second language corresponding to a language into which the input sentence is translated, wherein, if the first language is not the first typical language, the intra-category converting unit converts the input sentence into a sentence described in the first typical language of the first language category to which the first language belongs, wherein, if the first language and the second language belong to different language categories, the inter-category converting unit converts the sentence converted by the intra-category converting unit into a sentence described in the second typical language of a second language category to which the second language belongs, and wherein, if the second language is not the second typical language, the intra-category converting unit further converts the sentence converted by the inter-category converting unit into a sentence described in the second language.