To provide the main object detector of a camera capable of accurately detecting a main object.

The main object detector comprises: an image signal detector 19 having a plurality of detection areas; a luminance distribution detector 11 for detecting an object luminance corresponding to each area on the basis of image signals for the respective areas; a distance distribution detector 12 for detecting an object distance corresponding to each area on the basis of the image signals for the respective areas; a magnification distribution detector 13 for computing a photographing magnification corresponding to each area from the object distance information of the respective areas and the focus distance information of a photographing lens; a size/shape distribution detector 14 for detecting the size and shape of successive areas having the same luminance on the basis of the image signals for the respective areas; and a movement distribution detector 15 for detecting the movement distribution of an object corresponding to each area on the basis of a plurality of the image signals with timewise difference outputted from the image signal detector 19. The main object within an image is detected on the basis of the object luminance, the object distance, the photographing magnification and the movement distribution in each area.