An automatic focusing apparatus in which the quantity of auxiliary light can be precisely controlled regardless of conditions of an object to be taken is disclosed. The apparatus includes a passive AF sensor unit, a flash device and a main CPU which controls the flash device as an auxiliary light source for the focus detection, so that the flash device intermittently emits flashes of light. The main CPU increases emission time and emission time interval stepwise from the minimum value when the flash device intermittently emits flashes of light as the auxiliary light source upon detection of the focused state.