a focus condition detecting device which generated first and second light intensity distribution signals representing light intensity distributions on first and second arrays arranged to receive lights having passed through different areas of the exit pupil of an objective lens is arranged so as to divide the first light intensity distribution signal into a plurality of blocks . each of the portions of the first light intensity distribution signal belonging to the respective blocks is shifted relative to the second light intensity distribution signal by sequentially changing an amount of shift , so that correlations therebetween are calculated for finding the amount of shift providing the highest correlation . in accordance with the amount of shift found to provide the highest correlation through the correlation calculation with use of the portion of the first light intensity distribution signal belonging to one of the blocks , the shift range for the succeeding correlation calculation with use of the portion of the first light intensity distribution signal belonging to another one of the blocks is restricted to shorten the period of time required for the succeeding correlation calculation .