an automatic focusing device which is capable of movably setting a focus detecting area on an image sensing plane comprises a position detecting circuit which detects the position of a picture - taking object within the focus detecting area , a storage circuit which stores a plurality of object position data detected at different points of time by the position detecting circuit , a computing circuit which computes the moving position of the focus detecting area by smoothing the object position data stored by the storage circuit and object position data currently detected , and an area setting circuit which shifts the focus detecting area on the basis of the shifting position computed by the computing circuit .