1. An image capture device, comprising: an image pickup unit, having a lens and sensing elements, wherein the image pickup unit captures a plurality of temporary images from a plurality of visual angles of a scene in advance based on a plurality of scanning focal length values; and a processing circuit, connected to the image pickup unit, wherein the processing circuit obtains a temporary focal length value by weighing each of the scanning focal length values of the plurality of temporary images of each of the visual angles, and obtaining a weighting focal length value according to a function and the temporary focal length value, to control the image pickup unit to perform a panorama image capturing process according to the weighting focal length value, wherein the function is in accordance with following expression: L W = ∑ i = 1 m ⁢ L i ⁢ Q i Q tot in which L W is the weighting focal length value; L i is the temporary focal length value corresponding to each of the visual angles; m is a number of the visual angles; Q i is quantity of the temporary images corresponding to each of the visual angles; and Q tot is quantity of the total temporary images.