1. A text comparison apparatus, comprising: a text storage means for storing a plurality of texts; a text input means for inputting a text from the text storage means; a text element extraction means for extracting elements from the text obtained with the text input means; a text element counting means for counting how many of each of the text elements are included the text; a text element storage means for storing text elements and occurrence counts as sets; a text element input means for inputting text elements and their occurrence counts with regard to two texts from the text element storage means; and a similarity calculation means for calculating a similarity of the texts by dividing the sum of the occurrence counts of the text elements included in both of the two texts by the sum of the occurrence counts of all text elements in each of the texts.