1. A method for generating stereoscopic views from monoscopic endoscope images, comprises the following steps: obtaining monoscopic images, wherein the monoscopic images are obtained by capturing images of organs in an operating field via an endoscope; obtaining a background depth map of the operating field for each image; obtaining an instrument depth map corresponding to an instrument, wherein the instrument is inserted in a patient's body cavity for each image; merging the background depth map and the instrument depth map to generate an integrated depth map for each image; and generating stereoscopic views according to the monoscopic images and the corresponding integrated depth maps.