An automatic focus adjusting device which takes into account a change in the position of the image plane of an object caused by movement of the object during the focus adjusting operation time and makes a lens in focus to the moving object. The position of the image plane of the object after the focus adjusting operation time is foreseeing-calculated with the result of a past focus adjusting operation as a factor, and the current focus adjusting operation time is foreseen in conformity with the foreseeing-calculated value, and the position of the image plane of the object is again foreseeing-calculated with the foreseen time as a factor.