To easily form an image having high density and gradation by a method wherein a fusion type heat transfer ink sheet, on which an ink layer is carried, is faced against an image receiving sheet, on which a dye image having the gradation of a specified value in a transferred density, so as to form a binary transferred image having a specified value in density only at a heated part.

The image receiving layer surface of an image receiving sheet having an image receiving layer 2 on one side of a support 1 is faced to the ink layer surface of an ink sheet, which is produced by carrying an ink layer containing a sublimable or heat-diffusing dye on another support so as to produce a dye image 3 having the gradation, the transferred density of which ranges from 0 to D1 through an image-like heating from the support side of the ink sheet. Next, a fusion type heat transfer ink sheet, on which the ink layer is carried through a heat fusible binder containing a coloring material having the same color tone as the ink sheet, is faced to the image receiving sheet so as to form a binary transferred image 4 having the density of D2 only at a heated part through an image-like heating from the support side of the ink sheet. By combining the formations of the images 3 and 4, an image having the gradation, the density of which ranges from 0 to (D1+D2), is produced.