A calibration method of an image device includes at least two image capturing units included in the image device capturing at least two corresponding images; a processor executing distortion correction on the at least two corresponding images, extracting a plurality of feature points of a predetermined number of planes of an object from the at least two corresponding images, classifying the plurality of feature points according to each plane of the predetermined number of planes to accordingly calculate a point-to-point homography matrix corresponding to the each plane respectively to generate a rotation/translation matrix corresponding to the at least two image capturing units, generating a final rotation matrix corresponding to each image capturing unit of the at least two image capturing units according to the rotation/translation matrix, storing the final rotation matrix in a memory, and calibrating the each image capturing unit according to the final rotation matrix.