1. A text mining device, including: a text set storage unit configured to store a plurality of text obtained by forming a plurality of non-text data into the plurality of text; a reliability storage unit configured to store an all-class reliability of each of the plurality of text stored in said text set storage unit, said all-class reliability being derived from the formation of said plurality of non-text data into said plurality of text; a text mining unit configured to search the plurality of text for a plurality of text of a same class, where said plurality of text of the same class has a characteristic the same as the plurality of text stored in said text set storage unit; and a text selection unit configured to read a same-class reliability of each of said plurality of text of the same class searched by said text mining unit from said reliability storage unit, and configured to select a part of said plurality of text of the same class from the plurality of text of the same class based on the same-class reliability, wherein said text selection unit generates, for each of said plurality of text of the same class, a degree of assurance indicative of a degree of correlation between said plurality of text of the same class and said plurality of non-text data based on the same-class reliability of said plurality of text of the same class, and selects a portion of said plurality of text of the same class having the highest degree of assurance as said part of said plurality of text of the same class from among said plurality of text of the same class.