An edge vector extraction unit (122) extracts edge vectors from an input image, and a variable-magnification processing unit (123) performs smoothing/variable-magnification processing of the edge vectors. A vertex point adjustment unit (100) selects each of vertex points constituting an edge vector loop as a vertex point of interest, discriminates the directions of two vertex vectors, which sandwich the edge point of interest, and adjusts the coordinate position of the vertex point of interest sandwiched between the two edge vectors having a predetermined combination on the basis of the combination of the directions, thereby suppressing a deformation of an output image, which may be caused by the variable-magnification processing.