PURPOSE: To prevent a malfunction by making its operation effective, when only one touch position is touched, as a result of executing a retrieval twice.

CONSTITUTION: When a touch is detected continuously twice with regard to one of plural touch positions on a touch panel, its touch position is informed as a selected position. Accordingly, only in the case only one of plural touch positions is touched, its touch becomes effective. That is, in the case (a) the touch positions of two parts or more are touched, and in the case (b) the touch position is shifted, the result of detection is not informed. In such a manner, the malfunction is prevented.