PURPOSE: To provide a dictionary unregistered word attribute estimating device for estimating the semantic attribute and formal name of an abbreviated foreign word which appears for the first time in a sentence to be processed and is not registered in a dictionary.

CONSTITUTION: This dictionary unregistered word attribute estimating device has an abbreviated foreign word extracting means 3 for extracting an abbreviated foreign word in a Japanese sentence, an abbreviated foreign word estimation rule learning means 4 for learning a rule for recognizing an abbreviated foreign word not registered in a Japanese dictionary 6 when the extracted abbreviated word has been registered in the dictionary 6, an abbreviated foreign word estimation rule table 7 for storing the learned rule, and an abbreviated foreign word estimating means 5 for applying the rule stored in the table 7 when the abbreviated word concerned is not registered in the dictionary 6 and estimating the attribute of the abbreviated word.