1. A focusing method having depth-of-field adaptability and aperture adaptability, applying for an image capture unit including an image capture window, and comprising steps of: capturing a plurality of first images according to a plurality of objects contained in the acquirable field of said image capture window; extracting the image information of said plurality of first images for acquiring a plurality of distances between said plurality of objects and said image capture unit; obtaining a focus distance of said image capture unit according to said plurality of distances, and said focus distance being the average of said plurality of distances; and adjusting a first aperture to a second aperture according to a maximum value and a minimum value of said plurality of distances, and enabling said image capture unit to capture a second image according said plurality of objects and by means of said second aperture and said focus distance.