Feature points included in input images are extracted and matching information indicating mapping relationships for feature points included in different input images is generated. A reference image is selected among the input images based on the matching information. Valid images are determined among the input images by excluding noise images from the input images based on the matching information. A two-dimensional bundle adjustment is performed to generate synchronized images by aligning the valid images to the reference image. A merged image is generated by merging the reference image and the synchronized images. Image merging performance is enhanced by selecting the reference image highly correlated with the other input images and estimating exact homography based on the reference image.