A novel large-stage atomic force microscope (AFM) for nondestructive characterization of optical thin films is built. An open sample stage and a probe unit are employed to measure samples with large size and weight. Three optical thin films with large areas are imaged using this AFM without needing to cut the pieces apart. Experimental results show that the maximum scanning range for one single image can reach 20×20 (μm) while keeping a high resolution laterally and vertically. The maximum possible size of a sample is 600×1000 (mm). The new AFM is capable of performing wide-range and high-resolution characterizations of large samples such as large-area optical thin films.