1. An image stitching method, for use in an image processing device, the method comprising: utilizing the image processing device to receive a first video file and a second video file, wherein the first video file comprises at least one first image and a first audio track, and the second video file comprises at least one second image and a second audio track; calculating delay time between a first acoustic feature of the first audio track and a second acoustic feature of the second audio track and synchronizing the first image and the second image according to the delay time; converting the first image and the second image into a first adjusted image and a second adjusted image, respectively; and performing an image stitching process on the first adjusted image and the second adjusted image to generate a stitched image.