A quantitative image of a subject is obtained without being influenced by the distance from the subject by accurately measuring the absolute distance between the subject and the tip of a phototransmitter that radiates light onto the subject. There is provided an endoscopic observation apparatus (1) that includes, at the tip of an inserted member (6) to be disposed in a body cavity, a phototransmitter (12) that radiates light onto a subject opposing the tip and a photoreceptor (12) that receives observation light returning from the subject, an ultrasonic sensor (13) that measures the absolute distance between the inserted member (6) and the subject using oscillation of ultrasonic waves, a correcting unit (32) that corrects the luminance information of the observation light on the basis of the absolute-distance information obtained by the ultrasonic sensor (13), and an image generating unit (32) that generates an image of the subject on the basis of the luminance information of the observation light, corrected by the correcting unit (32).
