An auto-focus (AF) method adapted for an image capturing device includes following steps. When a first press signal generated by a user pressing a button of the image capturing device is detected, a local peak searching method is applied to perform an AF procedure. It is determined whether a second press signal generated by the user pressing the button is detected. If not, it is determined whether a first released signal generated by the user releasing the button is detected. The continuous pressing count is calculated according to the first released signal and the first press signal that are continuously generated. Whether the continuous pressing count is greater than a first threshold is determined. If yes, a global peak searching method is applied to perform the AF procedure. If not, the local peak searching method is still applied to perform the AF procedure.