1. A text anonymizing apparatus, comprising: a storage device which stores a plurality of pieces of text data, each including a character string; a data linking unit which classifies each of the plurality of pieces of text data into one of a plurality of kinds of linked data, in accordance with a classification condition, to classify a subset of the plurality of pieces of text data having a same classification condition together as pieces of linked data; a morpheme analysis unit which extracts a plurality of words included in the pieces of linked data classified by the data linking unit; an evaluating unit which extracts, among combinations of words including at least one of the extracted words, a combination of words in which the number of occurrences of the combination of words occurring within the pieces of linked data, is equal to or greater than a threshold; an anonymizing unit which anonymizes, among words included in a character string included in the pieces of linked data, original words matching at least some of the extracted words and not matching words forming the extracted combination of words, as anonymized words; and an output processing unit which outputs text data including the anonymized words substituted for the original words, to an output device.