PURPOSE: To provide the efficient translation processor by utilizing the conversion result of a compound word containing nouns before and behind an object of conversion to determine equivalents of the nouns at the time of conversion into a target language.

CONSTITUTION: A character set inputted by a keyboard, etc., is divided into words by the morpheme analyzing function of an original sentence analytic part 131 and a compound word which is a noun is detected among the divided words. Further, a conversion processor part 132 finds an equivalent of the target language corresponding to the compound word detected by the morpheme analyzing function and equivalents to the respective elements constituting the compound word. At this time, when plural equivalents to each element are obtained, optimum equivalents are selected among equivalents corresponding to the respective elements by optimum equivalent selection processing 134 according to the equivalent to the compound and stored in a translation conversion dictionary 16, etc. Then when each element appears alone behind the compound word, the conversion processing part 132 sets the equivalent as an equivalent corresponding to the element stored in the translation conversion dictionary 16, etc.