The present invention relates to a device for measuring object distance or an in-focus position used for a camera in which the object distance of focus adjusting condition are measured in a plurality of distance measuring areas in the photographing scene. The device is so constructed as to judge a main object from weight data in correspondence not only with the object distance of each distance measuring area but with the position thereof in the photographing scene. Further, when there is an object nearer than a predetermined distance, the main object is judged from whether the object has a size larger than a predetermined size in the photographing scene. Furthermore, it is judged from the difference between the object distances of adjacent distance measuring areas whether the objects are the same object.