Auto-focus method, device, and apparatus

An auto-focus method, device, and apparatus. The method comprises: acquiring a first image of an object to be photographed with an imaging component respectively when a lens is on at least two different positions (S101), wherein the at least two different positions are on the same plane in parallel with an imaging plane of the imaging component on which the respective first images are formed; determining, on the basis of the respective first images, an object distance of the object to be photographed with respect to the lens (S102); and determining, according to the object distance, a focus position of the lens (S103). The auto-focus method, device, and apparatus can simplify an auto-focus process and improves the auto-focus speed.