Abstract: An automatic focussing apparatus comprises a first drive element for repeatedly oscillating a movable reflecting mirror of an optical system of the range finder type, a second drive element for moving a focussing lens, a first signal generating component for producing a first signal when the amounts of light received by a stationary reflecting mirror and the movable reflecting mirror of the optical system are equal to each other, a second signal generating component for producing a second signal indicative of the position of the focussing lens, and a decision component for deciding the direction in which the focussing lens is to be moved in accordance with the relative timing of the first and the second signals.