This structure forming method comprises a first step and a second step. The first step includes: forming, using an electromagnetic wave heat converting material, a first pattern, which is a fine pattern, on a first surface of a medium that includes an expanding layer that expands when heated, the first surface being on the side where the expanding layer is provided; and then, causing sections of the expanding layer that correspond to the first pattern to expand by irradiating the electromagnetic wave heat converting material with electromagnetic waves. The second step includes: forming, using an electromagnetic wave heat converting material, a second pattern, which includes a coarser pattern than the first pattern, on a second surface of the medium, the second surface being on the opposite side from the side where the expanding layer is provided; and then, causing sections of the expanding layer that correspond to the second pattern to expand by irradiating the electromagnetic wave heat converting material wi
