1. A thermal transfer recording apparatus including a thermal head, comprising: image data acquisition means for acquiring original image data of RGB; color separation means for performing gradation conversion and then color separation for the original image data of RGB acquired by the image data acquisition means so as to obtain image data sets of C, M, Y, and K; contour expansion means for expanding the image data sets obtained by the color separation means by different numbers of pixels, respectively; shift means for shifting the image data sets, which have been expanded by the contour expansion means, by different numbers of pixels, respectively; dot conversion means for performing dot conversion processing for the image data sets shifted by the shift means; printing data generation means for superposing the image data sets processed by the dot conversion means so as to generate printing data; and printing means for printing the printing data generated by the printing data generation means so as to obtain a printed object.