1. A method of determining a shaken image using auto focusing (AF), the method comprising: calculating a first maximum AF value by performing AF on a preview image and storing the calculated AF value; sampling a captured image according to a resolution of the preview image; calculating a second maximum AF value by performing AF on the sampled captured image; comparing the stored first maximum AF value with the second maximum AF value; and determining whether the captured image is shaken or not based on a comparison result.