To easily perform a printing at a high speed on a plain paper or the like of which the surface is not smooth.

For this heat-transfer material 10, on the mold release layer side of a supporting body, a transfer layer is laminated. The transfer layer is constituted in such a manner that microcapsules enclosing a dye precursor substance and a photo- curing resin or the like, is mixed in a developer layer comprising a developer and a thermoplastic resin. When respective color beams of red, green and blue are emitted in order from an LED head 23, based on image data, on the transfer layer of the heat-transfer material 10 which is linearly carried, respective microcapsules which should color-develop into cyan, magenta and yellow, are cured by the numbers corresponding to the luminous energies for respective colors of red, green and blue. A thermal head 24 heats the heat-transfer material 10 while pressing the material 10 to a plain paper 18. Microcapsules, which have not been cured, are broken by the heat-pressing by the thermal head 24, and dye precursor substances inside flow out and react with the developer. Thus, respective images of yellow, magenta and cyan are color-developed and manifested at densities being inversely proportional to the luminous energies for respective colors of blue, green and red. Simultaneously with the manifestation, the transfer layer melts and is transferred onto the plain paper 18.