A first pattern P1 is formed with a first material for converting electromagnetic wave energy into heat energy, on a first surface BS of a print medium M including an expansion layer M2 that expands by heating. A second pattern P2 for expanding the expansion layer M2 to complement expansion of the expansion layer M2 by the first pattern P1 is formed with a second material for converting electromagnetic wave energy into heat energy, on a second surface FS which is an opposite surface of the print mediumM to the first surface BS and is closer to the expansion layer M2 than the first surface BS. The first material forming the first pattern P1 is irradiated with electromagnetic waves from the first surface BS. The second material forming the second pattern P2 is irradiated with electromagnetic waves from the second surface FS.