Provided are an image forming method and a corrugated cardboard. The image forming method includes applying a treatment liquid containing at least one kind of acidic compound and having a pH of equal to or lower than 2 onto a corrugated cardboard substrate of L*≤90, applying a first ink composition, which contains a coloring material and water and in which a total content of resin particles and wax particles is equal to or less than 2% by mass with respect to a total mass of the first ink composition, to a treatment liquid-applied surface of the corrugated cardboard substrate onto which the treatment liquid is applied by an ink jet method under a condition of an amount of a liquid droplet of equal to or greater than 10 picoliters, and applying a second ink composition, which contains a resin, a wax, and water and in which a content of a coloring material is equal to or smaller than 0.5% by mass with respect to a total mass of the second ink composition, onto the first ink composition applied to the corrugated cardboard substrate.