1. A text mining device, including: a text set storage unit for storing a plurality of texts obtained by forming a plurality of non-text data into texts; a reliability storage unit for storing, for each of a plurality of texts stored in said text set storage unit, a reliability of the text which is derived from formation of said non-text data from which the text originates into texts; a text mining unit for executing, with respect to a plurality of texts stored in said text set storage unit, text mining of searching a plurality of texts of the same class having the same characteristic from the plurality of texts; and a text selection unit for reading, for each text of the same class searched by said text mining unit, a reliability of the text from said reliability storage unit to select a part of texts of the same class from the plurality of texts of the same class based on the reliability.