An information input device includes an input panel including an illumination light source, a plurality of first light-receiving elements and one or more second light-receiving elements, the illumination light source emitting detection light for detecting an external proximity object, the plurality of first light-receiving elements receiving detection light emitted from the illumination light source and then reflected from the external proximity object, the second light-receiving elements for monitoring the intensity of the detection light; a correction section performing adaptive sensitivity correction on light-receiving signals obtained by the first light-receiving elements through use of an intensity monitor signal of detection light obtained by the second light-receiving element; and an image processing section obtaining object information about one or more of the position, shape and size of the external proximity object based on a picked-up image obtained from the light-receiving signals subjected to the sensitivity correction by the correction section.