Disclosed is an interpolation pixel value determining method for dividing a unit region including the contour of an object into reference unit sections for each line along a predetermined direction, to find, using a region interposed between the two reference unit sections as an interpolation unit section, an interpolation pixel value in the interpolation unit section, in which a luminance total and a center of gravity are calculated in each of the two reference unit sections with the interpolation unit section interposed therebetween, the estimated values of a luminance total and a center of gravity in the interpolation unit section are found from the luminance totals and the centers of gravity in the two reference unit sections, and each of interpolation pixel values in the interpolation unit section is determined such that the luminance total and the center of gravity in the interpolation unit section are respectively values close to the estimated values.