A ranging apparatus according to the present invention can execute accurate focusing even when photography is performed in, for example, an environment in which the background of a main subject to be photographed is a night view. This accurate focusing is executed by performing two pre-integration operations, one with light projection and the other without light projection, then comparing signal patterns obtained by the two pre-integration operations to thereby select a partial area of a line sensor, which shows a difference between the signal patterns obtained by the comparison, and mainly using an output from this area as a signal for ranging. Further, this ranging apparatus performs pre-emission before the ranging operation, using the line sensor to set the ranging area of the apparatus substantially equal to an image area to be shot, thereby determining the position of the main subject in the image area to be shot. Thus, the ranging apparatus can select a desired subject without focus lock operations.