A method for calibrating image defection of an image capturing device having a first and second lens, a focusing actuator, and a prestored first focusing step-to-focusing distance relation includes the following steps. A plurality of image sets are captured by the first and second lens, where each of the image sets includes a first and second image, and the images sets include a reference image set. It is detected whether the reference image set is defective. When the reference image set is detected to be defective, the first focusing step-to-focusing distance relation is calibrated according to a focusing step and a focusing distance corresponding to each of the image sets, where the focusing step corresponding to each of the image sets is the number of steps that the focusing actuator is required to move the first and second lens to a focusing position to generate each of the image sets.