PURPOSE: To measure a distance to a main object by measuring the contrast of plural zones within a photographing range, designating the zone where there is the main object and executing the range-finding operation thereof.

CONSTITUTION: A signal including plural linear picture elements and corresponding to received light quantity is generated by a photoelectric conversion part 1 (a1), inputted and stored in a memory part 2 (a2). The signal stored in the memory part 2 is inputted to a contrast arithmetic operation circuit 3. Then, a signal corresponding to the contrast (contrast information) is outputted out of the signals of the adjacent picture elements (a3). The information is inputted to an A/D circuit 4 and inputted to a microcomputer 5. By the microcomputer 5, an area where there is the main object is selected based on the inputted signal (a4). By the memory part 2, the signal of the selected area is fetched from the whole signals and transferred to the microcomputer 5 based on the instruction of the microcomputer 5 (a5). By the microcomputer 5, correlative arithmetic operation is executed (a6) and interpolation arithmetic operation is executed based on a correlation value. Then, the distance is calculated (a7).