An information acquisition apparatus (1, 115, 126) comprises: a first unit (2) including a photoreceiver (10) for receiving first reflected light reflected at an object (4), and outputting a signal corresponding to light intensity of the first reflected light and a second unit (3) separately provided from the first unit (2), the second unit (3) including a calibrator (36) having a stable reflectance and for outputting second reflected light to the photoreceiver (10), the second reflected light being used for comparing the light intensity of the first reflected light.
