Abstract: A touch panel input device includes a sensor for detecting that an operator's finger has approached toward a touch input key, to prevent the operator from performing an erroneous key input operation. The sensor includes a multiplicity of optical element pairs each made up of a light emitting diode for emitting a light beam and a photodetector receiving the light beam from the light emitting element. Light beams generated by the optical element pairs are arranged in the form of a matrix to form a detection plane. When the operator's finger traverses the detection plane, a cursor is displayed on the display screen at a position corresponding to the position of the finger on the detection plane. Accordingly, the operator can correct the movement of the finger toward a desired key position by observing the cursor.