An auto-focusing method for a camera is provided to reduce the time for an auto-focusing process by exposing a frame once, and improve the measurement accuracy by repeatedly performing the auto-focusing process. An auto-focusing method for a camera comprises the steps of: changing the distance between a focus of a lens system and a light receiving surface of an image sensor; forming one image frame by sequentially exposing pixels on the light receiving surface during the distance changing step; calculating an edge value for each sub block by setting plural sub blocks on the image frame; determining the maximum edge value from the calculated edge value; and detecting a focus position of the lens system based on the maximum edge value.
