An automatic focusing method includes the following steps: providing a digital camera module, which includes a lens member, an image sensor member, a distance-measuring member, a signal-processing member, a drive control member, and a drive member; measuring an object distance using the distance-measuring member, and transmitting the object distance to the signal-processing member for generating a control signal; the drive control member driving the drive member according to the control signal; and the drive member driving the image sensor member or the lens member to a position determined by the control signal. The step of providing the digital camera module includes: providing the lens member, the image sensor member and the distance-measuring member; measuring a depth of focus of the lens member; establishing a range of error of movement of the drive member; and selecting a suitable signal-processing member, drive control member, and drive member.