1. A data processing device comprising: a display unit; a touch panel unit configured to detect a touch operation and output detection information; and at least one processor configured to implement: a flick detection unit configured to detect a direction of a flick from the detection information of the touch panel unit; a label determination unit configured to determine a label representing a category to which content belongs, based on the direction of the flick; and a teacher data generation unit configured to display the content on the display unit, and generate teacher data including the content and the label determined by the label determination unit, wherein the flick detection unit is further configured to detect the direction and a speed of a flick from the detection information of the touch panel unit, the label determination unit is further configured to determine the label representing the category to which the content belongs and a certainty factor of the label, based on the direction and the speed of the flick, and the teacher data generation unit is further configured to generate the teacher data including the displayed content and the label and the certainty factor determined by the label determination unit.