An apparatus and method for controlling exposure of a digital camera with high precision by setting a proper exposure amount by emitting auxiliary light during auto-focusing, detecting the luminance level of an object, and carrying out an exposure controlling operation. The apparatus detects the luminance level of an object in an AE frame under the outside light prior to emitting the auxiliary light, and detects again the luminance level of the object in an AF frame under the auxiliary light after emitting the auxiliary light. The apparatus further performs an exposure controlling operation based on the luminance level in the AE frame when it has been determined that the exposure amount of the AF frame has increased markedly in a determining step, or based on the luminance level in the AF frame when it has been determined that the exposure amount of the AF frame has not increased markedly in the determining step.