An optical monitoring apparatus comprising: a plurality of light sources; light irradiating means for irradiating a plurality of lights, optical axes of which are coincide with each other, emitted from the plurality of light sources to an area to be monitored, wherein the light irradiating means irradiates at least one of the plurality of lights and at least another one of the plurality of lights to the area to be monitored with mutually different beam diameters; light reception means for receiving reflected lights of the plurality of light beams incident from the area to be monitored; distance measuring means for measuring, for each of the plurality of lights, a distance to an object present in the area to be monitored based on the reflected lights; and feature extracting means for extracting a feature of the object present in the area to be monitored based on results of measurement of the distance for the plurality of lights measured by the distance measuring means, and_ wherein the plurality of lights are irradiated toward the area to be monitored in a plurality of directions, and wherein the feature extracting means extracts a feature with respect to a size of an object present in the area to be monitored based on a result of measurement of the distance, for each of the plurality of directions, for the reflected light of a light irradiated from the light irradiating means with a first beam diameter among the plurality of lights irradiated in a plurality of directions and a result of measurement of the distance, for each of the plurality of directions, for the reflected light of a light irradiated from the light irradiating means with a second beam diameter smaller than the first beam diameter. a plurality of light sources; light irradiating means for irradiating a plurality of lights, optical axes of which are coincide with each other, emitted from the plurality of light sources to an area to be monitored, wherein the light irradiating means irradiates at least one of the plurality of lights and at least another one of the plurality of lights to the area to be monitored with mutually different beam diameters; light reception means for receiving reflected lights of the plurality of light beams incident from the area to be monitored; distance measuring means for measuring, for each of the plurality of lights, a distance to an object present in the area to be monitored based on the reflected lights; and feature extracting means for extracting a feature of the object present in the area to be monitored based on results of measurement of the distance for the plurality of lights measured by the distance measuring means, and_ wherein the plurality of lights are irradiated toward the area to be monitored in a plurality of directions, and wherein the feature extracting means extracts a feature with respect to a size of an object present in the area to be monitored based on a result of measurement of the distance, for each of the plurality of directions, for the reflected light of a light irradiated from the light irradiating means with a first beam diameter among the plurality of lights irradiated in a plurality of directions and a result of measurement of the distance, for each of the plurality of directions, for the reflected light of a light irradiated from the light irradiating means with a second beam diameter smaller than the first beam diameter.