To provide an automatic focus detector capable of more accurately detecting out-of-focus amount by judging the distance from the optical axis of an image reforming lens in sensor data and correcting the out-of-focus amount in accordance with the distance.

An area sensor 6 is scanned by a sensor driving means 8 so as to read in the charge of a pair of subject images. An out-of-focus amount arithmetic operation means 7 calculates the out-of-focus amount from transferred stored data concerning all the lines of the area sensor 6, and further an optical axis deviation calculation means 9 calculates the distance from the optical axis of the image reforming lens. Thus, an out-of-focus amount correction means 10 selects a correction block, calculates correction data by a corresponding correction expression, and subtracts the correction data from the out-of-focus amount calculated previously so as to perform correction. The out-of-focus amount is accurately detected concerning all the areas.