1. A lesion detecting method for breast image in a rotating manner, comprising: obtaining a set of breast image in the rotating manner, wherein the set of breast image in the rotating manner comprises a plurality of sub breast images; reconstructing the sub breast images to generate a reconstructed breast image; and comparing the reconstructed breast image with the set of breast image in the rotating manner without being reconstructed to confirm at least one lesion position, comprising: performing region segment to the set of breast image in the rotating manner without being reconstructed to generate a region segment image; determining at least one suspicious lesion region in the region segment image; performing a false-positive reduction operation to the at least one suspicious lesion region to determine the at least one lesion position; and determining whether a connected lesion region exists in the reconstructed breast image according to the at least one lesion position, so as to confirm the at least one lesion position.